The impact of social complexity on the visual exploration of others' actions in preschoolers with autism spectrum disorder

BACKGROUND

Typical development of socio-communicative skills relies on keen observation of others. It thus follows that decreased social attention negatively impacts the subsequent development of socio-communicative abilities in children with autism spectrum disorders (ASD). In addition, studies indicate that social attention is modulated by context and that greater social difficulties are observed in more socially demanding situations. Our study aims to investigate the effect of social complexity on visual exploration of others' actions in preschoolers.

METHODS

To investigate the impact of social complexity, we used an eye-tracking paradigm with 26 typically developing preschoolers (TD, age = 3.60 ± 1.55) and 37 preschoolers with ASD (age = 3.55 ± 1.21). Participants were shown videos of two children engaging in socially simple play (parallel) versus socially complex play (interactive). We subsequently quantified the time spent and fixation duration on faces, objects, bodies, as well as the background and the number of spontaneous gaze shifts between socially relevant areas of interest.

RESULTS

In the ASD group, we observed decreased time spent on faces. Social complexity (interactive play) elicited changes in visual exploration patterns in both groups. From the parallel to the interactive condition, we observed a shift towards socially relevant parts of the scene, a decrease in fixation duration, as well as an increase in spontaneous gaze shifts between faces and objects though there were fewer in the ASD group.

LIMITATIONS

Our results need to be interpreted cautiously due to relatively small sample sizes and may be relevant to male preschoolers, given our male-only sample and reported phenotypic differences between males and females.

CONCLUSION

Our results suggest that similar to TD children, though to a lesser extent, visual exploration patterns in ASD are modulated by context. Children with ASD that were less sensitive to context modulation showed decreased socio-communicative skills or higher levels of symptoms. Our findings support using naturalistic designs to capture socio-communicative deficits in ASD.

The potential of δ2Hn-alkanes and δ18Osugar for paleoclimate reconstruction - A regional calibration study for South Africa

The hydrogen isotopic composition of leaf wax-derived n-alkanes (δ²H_n-alkanes) is a widely applied proxy for (paleo)climatic changes. It has been suggested that the coupling with the oxygen isotopic composition of hemicellulose-derived sugars (δ¹⁸O_sugar) - an approach dubbed 'paleohygrometer' - might allow more robust and quantitative (paleo)hydrological reconstructions. However, the paleohygrometer remains to be evaluated and tested regionally. In this study, topsoil samples from South Africa, covering extensive environmental gradients, are analysed. δ²H_n-alkanes correlates significantly with the isotopic composition of precipitation (δ²H_p), whereas no significant correlation exists between δ¹⁸O_sugar and δ¹⁸O_p. The apparent fractionation (ε_app) is the difference between δ²H_n-alkanes and δ²H_p (ε_{app 2H}) and δ¹⁸O_sugar and δ¹⁸O_p (ε_{app 18O}), respectively, and integrates i) isotopic enrichment due to soil water evaporation, ii) leaf (and xylem) water transpiration and iii) biosynthetic fractionation. We find no correlation of ε_{app 18O} nor for ε_{app 2H} with temperature, and no correlation of ε_{app 2H} with potential evapotranspiration and an aridity index. By contrast, ε_{app 18O} correlates significantly with both potential evapotranspiration and the aridity index. This highlights the strong effect of evapotranspirative enrichment on δ¹⁸O_sugar. In study areas without plant predominance using Crassulacean Acid Metabolism (CAM), coupling δ¹⁸O_sugar and δ²H_n-alkanes enables to reconstruct δ²H_p and δ¹⁸O_p with an offset of Δδ²H = 6 ± 27‰ and Δδ¹⁸O = 0.8 ± 3.7‰, respectively, as well as relative humidity (RH) with an offset of ΔRH = 6 ± 17%. The paleohygrometer does, however, not work well for our study areas where CAM plants prevail (reconstructed δ¹⁸O_p, δ²H_p and RH are off by 3.1‰, 27.2‰ and 31.7%). This probably reflects plant-specific (phenological) adaptations and/or post-photosynthetic exchange reactions related to CAM metabolism. Overall, our findings corroborate that δ²H_n-alkanes and δ¹⁸O_sugar are valuable proxies, and the paleohygrometer is a promising approach for paleoclimate reconstructions in southern Africa.

Circulating breast-derived DNA allows universal detection and monitoring of localized breast cancer

BACKGROUND

Tumor-derived circulating cell-free DNA (cfDNA) is present in the plasma of individuals with cancer. Assays aimed at detecting common cancer mutations in cfDNA are being developed for the detection of several cancer types. In breast cancer, however, such assays have failed to detect the disease at a sensitivity relevant for clinical use, in part due to the absence of multiple common mutations that can be co-detected in plasma. Unlike individual mutations that exist only in a subset of tumors, unique DNA methylation patterns are universally present in cells of a common type and therefore may be ideal biomarkers. Here we describe the detection and quantification of breast-derived cfDNA using a breast-specific DNA methylation signature.

PATIENTS AND METHODS

We collected plasma from patients with localized breast cancer before and throughout treatment with neoadjuvant chemotherapy and surgery (N = 235 samples).

RESULTS

Pretreatment breast cfDNA was detected in patients with localized disease with a sensitivity of 80% at 97% specificity. High breast cfDNA levels were associated with aggressive molecular tumor profiles and metabolic activity of the disease. During neoadjuvant chemotherapy, breast cfDNA levels decreased dramatically. Importantly, the presence of breast cfDNA towards the end of the chemotherapy regimen reflected the existence of residual disease.

CONCLUSION

We propose that breast-specific cfDNA is a universal and powerful marker for the detection and monitoring of breast cancer.

Does differential visual exploration contribute to visual memory impairments in 22q11.2 microdeletion syndrome?

BACKGROUND

Chromosome 22q11.2 microdeletion syndrome (22q11.2DS) is a genetic syndrome characterised by a unique cognitive profile. Individuals with the syndrome present several non-verbal deficits, including visual memory impairments and atypical exploration of visual information. In this study, we seek to understand how visual attention may contribute to memory difficulties in 22q11.2DS by tracking eye movements during the encoding phase of a visual short-term memory task.

METHOD

Eye movements were recorded during a computerised version of the multiple-choice Benton Visual Retention Test, which consisted of exploring and then recognising complex visual stimuli. Seventy-four participants affected by 22q11.2DS were compared with 70 typically developing participants.

RESULTS

Participants with 22q11.2DS performed less well than healthy controls on the task and spent more time and fixations on the principal (larger central) figures and less time and fixations on the smaller peripheral figures within the stimuli.

CONCLUSIONS

This study is the first to investigate visual attention in 22q11.2DS during a memory task. The results delineate impaired processes during encoding that affect visual memory performance. The findings may be especially useful for informing interventions intended to boost visual learning in patients with 22q11.2DS.

Understanding others: a pilot investigation of cognitive and affective facets of social cognition in patients with 22q11.2 deletion syndrome (22q11DS)

BACKGROUND

Although significant impairments in the affective and cognitive facets of social cognition have been highlighted in patients with 22q11.2 deletion syndrome (22q11DS) in previous studies, these domains have never been investigated simultaneously within the same group of participants. Furthermore, despite theoretical evidence, associations between these two processes and schizotypal symptoms or social difficulties in this population have been scarcely examined.

METHODS

Twenty-nine participants with 22q11DS and 27 typically developing controls (N = 5 siblings; N = 22 unrelated controls) aged between 11 and 21 years participated in the study. Both groups were matched for age and gender distribution. Two computerized social cognition tasks evaluating perspective and emotion recognition abilities were administered to all participants. The levels of schizotypal trait expression and social functioning were further investigated in both groups, based on a validated self-report questionnaire (Schizotypal Personality Questionnaire) and parental interview (Vineland Adaptive Behavior Scales).

RESULTS

Participants with 22q11DS exhibited lower perspective-taking and emotion recognition capacities than typically developing controls. The two socio-cognitive dimensions investigated here were further correlated in healthy controls. The efficiency of perspective-taking processes (response time) was marginally related to the degree of schizotypal trait expression in patients with 22q11DS.

CONCLUSIONS

This study first provides support for significant deficits in two core facets of social cognition in 22q11DS. The associations observed between the experimental tasks and measures of social functioning or schizotypal symptoms in 22q11DS open promising research avenue, which should be more deeply investigated in future studies.

Effects of ageing and senescence on pancreatic β-cell function

Ageing is generally associated with deterioration of organ function and regenerative potential. In the case of pancreatic β-cells, an age-related decline in proliferative potential is well documented, and was proposed to contribute to the increased prevalence of type 2 diabetes in the elderly. The effects of ageing on β-cell function, namely glucose-stimulated insulin secretion (GSIS), have not been studied as extensively. Recent work revealed that, surprisingly, β-cells of mature mice and humans secrete more insulin than young β-cells in response to high glucose concentrations, potentially serving to counteract age-related peripheral insulin resistance. This functional change appears to be orchestrated by p16(Ink4A) -driven cellular senescence and downstream remodelling of chromatin structure and DNA methylation, enhancing the expression of genes controlling β-cell function. We propose that activation of the cellular senescence program drives life-long functional maturation of β-cells, due to β-cell hypertrophy, enhanced glucose uptake and more efficient mitochondrial metabolism, in parallel to locking these cells in a non-replicative state. We speculate that the beneficial aspects of this process can be harnessed to enhance GSIS. Other age-related mechanisms, which are currently poorly understood, act to increase basal insulin secretion levels also in low glucose conditions. This leads to an overall reduction in the amplitude of insulin secretion between low and high glucose at old age, which may contribute to a deterioration in metabolic control.

Identification of a G-Protein Subunit-α11 Gain-of-Function Mutation, Val340Met, in a Family With Autosomal Dominant Hypocalcemia Type 2 (ADH2)

Autosomal dominant hypocalcemia (ADH) is characterized by hypocalcemia, inappropriately low serum parathyroid hormone concentrations and hypercalciuria. ADH is genetically heterogeneous with ADH type 1 (ADH1), the predominant form, being caused by germline gain-of-function mutations of the G-protein coupled calcium-sensing receptor (CaSR), and ADH2 caused by germline gain-of-function mutations of G-protein subunit α-11 (Gα11 ). To date Gα11 mutations causing ADH2 have been reported in only five probands. We investigated a multigenerational nonconsanguineous family, from Iran, with ADH and keratoconus which are not known to be associated, for causative mutations by whole-exome sequencing in two individuals with hypoparathyroidism, of whom one also had keratoconus, followed by cosegregation analysis of variants. This identified a novel heterozygous germline Val340Met Gα11 mutation in both individuals, and this was also present in the other two relatives with hypocalcemia that were tested. Three-dimensional modeling revealed the Val340Met mutation to likely alter the conformation of the C-terminal α5 helix, which may affect G-protein coupled receptor binding and G-protein activation. In vitro functional expression of wild-type (Val340) and mutant (Met340) Gα11 proteins in HEK293 cells stably expressing the CaSR, demonstrated that the intracellular calcium responses following stimulation with extracellular calcium, of the mutant Met340 Gα11 led to a leftward shift of the concentration-response curve with a significantly (p < 0.0001) reduced mean half-maximal concentration (EC50 ) value of 2.44 mM (95% CI, 2.31 to 2.77 mM) when compared to the wild-type EC50 of 3.14 mM (95% CI, 3.03 to 3.26 mM), consistent with a gain-of-function mutation. A novel His403Gln variant in transforming growth factor, beta-induced (TGFBI), that may be causing keratoconus was also identified, indicating likely digenic inheritance of keratoconus and ADH2 in this family. In conclusion, our identification of a novel germline gain-of-function Gα11 mutation, Val340Met, causing ADH2 demonstrates the importance of the Gα11 C-terminal region for G-protein function and CaSR signal transduction. © 2016 American Society for Bone and Mineral Research.

Visual processing of emotional dynamic faces in 22q11.2 deletion syndrome

INTRODUCTION

The 22q11.2 deletion syndrome (22q11DS) is a neurogenetic syndrome. Individuals affected by this syndrome present poor social functioning and a high risk for the development of psychiatric disorders. Accurate emotion recognition and visual exploration of faces represent important skills for appropriate development of social cognition in individuals with 22q11DS. For these reasons, there is elevated interest in establishing relevant ways to test the mechanisms associated with emotion recognition in patients with 22q11DS.

METHODS

This study investigated emotional recognition and visual exploration of emotional faces in persons with 22q11DS, with a dynamic emotion task using an eye-tracking device. To our knowledge, no previous studies have used emotional dynamic stimuli with 22q11DS, despite improved ecological validity of dynamic stimuli compared with static images. Furthermore, these stimuli provide the opportunity to collect reaction times, as indicators of the emotional intensity necessary for identifying each emotion.

RESULTS

In our task, we observed comparable accuracy in emotion recognition in the 22q11DS and healthy control groups. However, individuals with 22q11DS were slower to recognise the emotions. They also spent less time looking at the nose during happy and fearful faces.

CONCLUSIONS

These results suggest that individuals with 22q11DS may need either more time or more pronounced emotional cues to correctly label facial expressions.

Glucose metabolism: key endogenous regulator of β-cell replication and survival

Recent studies in mice have shown that pancreatic β-cells have a significant potential for regeneration, suggesting that regenerative therapy for diabetes is feasible. Genetic lineage tracing studies indicate that β-cell regeneration is based on the replication of fully differentiated, insulin-positive β-cells. Thus, a major challenge for this field is to identify and enhance the molecular pathways that control β-cell replication and mass. We review evidence, from human genetics and mouse models, that glucose is a major signal for β-cell replication. The mitogenic effect of blood glucose is transmitted via glucose metabolism within β-cells, and through a signalling cascade that resembles the pathway for glucose-stimulated insulin secretion. We introduce the concept that the individual β-cell workload, defined as the amount of insulin that an individual β-cell must secrete to maintain euglycaemia, is the primary determinant of replication, survival and mass. We also propose that a cell-autonomous pathway, similar to that regulating replication, appears to be responsible for at least some of the toxic effects of glucose on β-cells. Understanding and uncoupling the mitogenic and toxic effects of glucose metabolism on β-cells may allow for the development of effective regenerative therapies for diabetes.

Age- and puberty-dependent association between IQ score in early childhood and depressive symptoms in adolescence

BACKGROUND

Lower cognitive functioning in early childhood has been proposed as a risk factor for depression in later life but its association with depressive symptoms during adolescence has rarely been investigated. Our study examines the relationship between total intelligence quotient (IQ) score at age 8 years, and depressive symptoms at 11, 13, 14 and 17 years.

METHOD

Study participants were 5250 children and adolescents from the Avon Longitudinal Study of Parents and their Children (ALSPAC), UK, for whom longitudinal data on depressive symptoms were available. IQ was assessed with the Wechsler Intelligence Scale for Children III, and self-reported depressive symptoms were measured with the Short Mood and Feelings Questionnaire (SMFQ).

RESULTS

Multi-level analysis on continuous SMFQ scores showed that IQ at age 8 years was inversely associated with depressive symptoms at age 11 years, but the association changed direction by age 13 and 14 years (age-IQ interaction, p<0.0001; age squared-IQ interaction, p<0.0001) when a higher IQ score was associated with a higher risk of depressive symptoms. This change in IQ effect was also found in relation to pubertal stage (pubertal stage-IQ interaction, 0.00049<p=0.038). At age 17 years, however, sex-specific differences emerged (sex-age squared-IQ interaction, p=0.0075). Whilst the risk effect of higher childhood IQ scores for depressive symptoms declined in females, and some analyses even supported an inverse association by age 17 years, it persisted in males.

CONCLUSIONS

Our results suggest that the association between cognitive ability in childhood and depressive symptoms in adolescence varies according to age and/or pubertal stage.

[Time processing in the velo-cardio-facial syndrome (22q11) and its link with the caudate nucleus]

INTRODUCTION

Velocardiofacial syndrome (VCFS) is a neurogenetic disorder caused by a microdeletion on chromosome 22q11. Among other cognitive impairments and learning difficulties, affected individuals show difficulties in estimating time intervals (Debbané et al., 2005). Interestingly, neuroimaging studies have found an increased volume of the basal ganglia of people with VCFS (Eliez et al., 2002; Kates et al., 2004; Campbell et al., 2006). Given that the caudate nucleus represents a central component of the cerebral network underlying temporal perception skills, the present report proposes to examine potential relationships between cerebral alteration to the caudate nucleus and time estimation in individuals with VCFS.

METHODS

A group of 30 patients with VCFS and 38 age-matched healthy individuals participated in time perception and time reproduction tasks. In the time perception task, individuals listened to two sequential stimuli and had to choose the longer of both stimuli by pressing a button. In the time reproduction task, subjects listened to a succession of sounds and once this succession had stopped they had to reproduce the same rhythm with their dominant index. Cerebral MRI images were also obtained for each participant. A manual tracing procedure was performed to measure the basal ganglia volume.

RESULTS

Participants with VCFS demonstrated significantly poorer performances during the time perception and time reproduction tasks in comparison to the control participants. Further, increased volume of the caudate nucleus was found in individuals with VCFS. Correlational analyses revealed a significant relationship between the caudate nucleus's volume and the performances obtained in the time perception task for control participants. This correlation was not found for individuals with VCFS.

CONCLUSION

The present results suggest that cerebral alterations to the caudate nucleus in VCFS may alter the temporal perception function it sustains.

Perinatal folate-related exposures and risk of psychotic symptoms in the ALSPAC birth cohort

BACKGROUND

It is unclear to what extent non-clinical psychotic experiences during childhood and adolescence share underlying aetiological mechanisms with schizophrenia. One candidate mechanism for schizophrenia involves the epigenetic status of the developing fetus, which depends on the internal folate-status of mother and child. Our study examines the relationships between multiple determinants of perinatal folate-status and development of psychotic experiences in adolescence.

METHODS

Study participants were up to 5344 mother-child pairs from the Avon Longitudinal Study of Parents and their Children, UK, with information on maternal and/or child MTHFR C677T genotype, maternal folate intake (supplementation at 18/32- weeks gestation; dietary intake at 32- weeks gestation) and psychosis-like symptoms (PLIKS) for children assessed at age 12.

RESULTS

Nominal evidence was observed that maternal folate supplementation at 18 weeks increased the odds of PLIKS in children (odds ratio(OR)=1.34; 95%-CI:[1.00;1.76]) and, consistent with this, that children of MTHFR C667T TT homozygous mothers had decreased odds of PLIKS (OR=0.72; 95%CI:[0.50;1.02]; recessive model) with strongest effects in boys (OR=0.44, 95%-CI:[0.22;0.79]; sex-specific p=0.029). None of the reported effects remained significant when corrected for multiple testing.

CONCLUSIONS

Overall, this study found no support that maternal/child MTHFR C677T genotype and maternal folate intake during pregnancy contribute to common aetiological pathways that are shared between schizophrenia and non-clinical psychotic symptoms in adolescents, assuming that decreased folate-status increases schizophrenia risk.

Impact of polymorphisms in WFS1 on prediabetic phenotypes in a population-based sample of middle-aged people with normal and abnormal glucose regulation

AIM/HYPOTHESIS

Recently, variants in WFS1 have been shown to be associated with type 2 diabetes. We aimed to examine metabolic risk phenotypes of WFS1 variants in glucose-tolerant people and in individuals with abnormal glucose regulation.

METHODS

The type 2 diabetes-associated WFS1 variant rs734312 (His611Arg) was studied in the population-based Inter99 cohort involving 4,568 glucose-tolerant individuals and 1,471 individuals with treatment-naive abnormal glucose regulation, and in an additional 3,733 treated type 2 diabetes patients.

RESULTS

The WFS1 rs734312 showed a borderline significant association with type 2 diabetes with directions and relative risks consistent with previous reports. In individuals with abnormal glucose regulation, the diabetogenic risk A allele of rs734312 was associated in an allele-dependent manner with a decrease in insulinogenic index (p = 0.025) and decreased 30-min serum insulin levels (p = 0.047) after an oral glucose load. In glucose-tolerant individuals the same allele was associated with increased fasting serum insulin concentration (p = 0.019) and homeostasis model assessment of insulin resistance (HOMA-IR; p = 0.026). To study the complex interaction of WFS1 rs734312 on insulin release and insulin resistance we introduced Hotelling's T (2) test. Assuming bivariate normal distribution, we constructed standard error ellipses of the insulinogenic index and HOMA-IR when stratified according to glucose tolerance status around the means of each WFS1 rs734312 genotype level. The interaction term between individuals with normal glucose tolerance and abnormal glucose regulation on the insulinogenic index and HOMA-IR was significantly associated with the traits (p = 0.0017).

CONCLUSIONS/INTERPRETATION

Type 2 diabetes-associated risk alleles of WFS1 are associated with estimates of a decreased pancreatic beta cell function among middle-aged individuals with abnormal glucose regulation.

Source monitoring for actions in adolescents with 22q11.2 deletion syndrome (22q11DS)

BACKGROUND

Source monitoring consists in identifying the origin of mental events. Recent research suggests that confusions over internally generated mental events may represent a cognitive marker for increased proneness to psychotic symptoms and disorders. We have examined source monitoring for actions in adolescents with the 22q11.2 deletion syndrome (22q11DS), a neurogenetic disease associated with high rates of schizophrenia during adulthood, and expected to observe source monitoring deficits in comparison to IQ-matched and typically developing controls.

METHOD

Eighteen adolescents with 22q11DS, 17 adolescents matched for age and IQ, and also 17 adolescents matched for age participated in this study. Our adapted action monitoring paradigm asked subjects to visualize a series of actions in three different conditions: (1) visualize themselves performing the action; (2) visualize the experimenter performing the action; or (3) simply repeat the action statements without visualization of the action performer.

RESULTS

The adolescents with 22q11DS performed adequately in terms of recognition (hits), but in comparison to both control groups, they committed more source confusions on correctly recognized items. Further examination revealed that the adolescents were more likely to demonstrate confusions between exterior sources in which the self was not involved.

CONCLUSIONS

Source monitoring deficits can be observed in adolescents with 22q11DS, a syndrome putting them at high risk for developing schizophrenia. These deficits are discussed in terms of early cognitive processes associated with genetic risk for schizophrenia.

Effects of a functional COMT polymorphism on brain anatomy and cognitive function in adults with velo-cardio-facial syndrome

BACKGROUND

Velo-cardio-facial syndrome (VCFS) is associated with deletions at chromosome 22q11, abnormalities in brain anatomy and function, and schizophrenia-like psychosis. Thus it is assumed that one or more genes within the deleted region are crucial to brain development. However, relatively little is known about how genetic variation at 22q11 affects brain structure and function. One gene on 22q11 is catechol-O-methyltransferase (COMT): an enzyme that degrades dopamine and contains a functional polymorphism (Val158Met) affecting enzyme activity. Here, we investigated the effect of COMT Val158Met polymorphism on brain anatomy and cognition in adults with VCFS.

METHOD

The COMT Val158Met polymorphism was genotyped for 26 adults with VCFS on whom DNA was available. We explored its effects on regional brain volumes using hand tracing approaches; on regional grey- and white-matter density using computerized voxel-based analyses; and measures of attention, IQ, memory, executive and visuospatial function using a comprehensive neuropsychological test battery.

RESULTS

After corrections for multiple comparisons Val-hemizygous subjects, compared with Met-hemizygotes, had a significantly larger volume of frontal lobes. Also, Val-hemizygotes had significantly increased grey matter density in cerebellum, brainstem, and parahippocampal gyrus, and decreased white matter density in the cerebellum. No significant effects of COMT genotype on neurocognitive performance were found.

CONCLUSIONS

COMT genotype effects on brain anatomy in VCFS are not limited to frontal regions but also involve other structures previously implicated in VCFS. This suggests variation in COMT activity is implicated in brain development in VCFS.

Long-term neurodevelopmental outcome in conservatively treated congenital hyperinsulinism

BACKGROUND

Congenital hyperinsulinism (CH) is treated surgically in many centers (near-total and partial pancreatectomy for diffuse and focal disease respectively). Most patients treated with near-total pancreatectomy developed diabetes during childhood/puberty. CH patients are at increased risk of neurodevelopmental disorders, some being severe, which are reported to occur in 14-44% of patients from highly heterogenous cohorts. Over the last few decades, we have treated children with CH conservatively without surgery. The aim of this study was to assess the neurodevelopmental outcome of these patients.

DESIGN AND METHODS

The study included 21 Ashkenazi CH medically treated patients: 11 homozygotes (diffuse disease) and 9 heterozygotes with mutations on the paternal allele (presumed focal disease). The mean age was 13.7 years (range 8-23). Neurodevelopmental outcomes were assessed by telephone interviews of parents, using a standard questionnaire. Closest age siblings of CH patients served as controls.

RESULTS

Ten CH patients had perinatal seizures of short duration. Four had post-neonatal seizures, which remitted entirely. During early childhood, four patients (19%) had hypotonia, eight (38%) had fine motor problems, seven (33%) had gross motor problems (clumsiness), and one had mild cerebral palsy. Three patients (14%) had speech problems. Eight patients required developmental therapy, compared to one in the control group. Most of these problems were resolved by age 4-5 years. At school age, all were enrolled in regular education, some excelled in their studies, 6 out of 21 patients (29%) had learning problems (2 out of 21 controls). None had overt diabetes.

CONCLUSIONS

Good neurodevelopmental outcome was observed in our conservatively treated CH patients, with no diabetes as reported in patients undergoing pancreatectomy.

Alkylphenols in sediments of the Atlantic Rainforest south-west of São Paulo, Brazil

Concentrations of technical 4-nonylphenol, 4-n-octylphenol, and 4-tert-octylphenol were investigated in surface water and sediment samples of four reservoirs southwest of São Paulo. Three of them (Takimoto 1, Takimoto 2, Pedro) were established in intensively cropped landscapes, one (Morro Grande) was surrounded by dense forests. Total alkylphenol concentrations in sediments generally ranged between 1 and 10 microgkg-1dw with 4-tert-octylphenol being the dominant alkylphenol. Because 4-tert-octylphenol concentration patterns at Takimoto 2, Pedro, and in the Morro Grande forest reservoir were found to be quite similar (upto 5 microgkg-1dw), this value is considered as the ubiquitous background level. In contrast, the Takimoto 1 sediments showed significantly higher 4-tert-octylphenol concentrations, possibly due to accelerated inputs from adjacent intensively cropped fields. Analysed alkylphenols were not detectable in water samples.

Bacterial contamination of filtered intraoral bone chips

Intraoral bony defects can be filled with bony particles that are collected in a titanium filter. The aim of this study was to determine quantitatively and qualitatively the degree of this contamination. Over a period of 3 months, bony particles were collected from 50 patients undergoing oral surgery. The bony particles were scraped off the filter, resuspended, and incubated aerobically and anaerobically on human blood agar media. Colony forming units (CFU) were determined as well as the most common species of bacteria. All samples showed anaerobic and aerobic growth. After anaerobic incubation in 44 samples the number of bacteria was higher (38) or equal (six) to that after aerobic incubation. On average, 435,000 CFU (aerobic) and 1,013,000 CFU (anaerobic) per sample were found. The most frequently identified bacteria belonged to Veillonella spp. in the anaerobic and to Streptococcus oralis in the aerobic cultures. In 43 samples black-pigmented colonies were detected. Only bacteria common in the oral cavity were identified. Prophylactic antibiotic therapy may be indicated when using filtered bony particles for intraoral augmentation procedures.

A multiple case study of verbal short-term memory in velo-cardio-facial syndrome

BACKGROUND

Velo-cardio-facial syndrome (VCFS, 22q11.2 deletion) is characterized by severely delayed language development. The current study explored the integrity of verbal short-term memory (STM), a cognitive function critically involved in language development, in eight children with VCFS.

METHODS

Using a multiple case study design, we presented a series of STM tasks exploring immediate serial recall for word and non-word lists to eight children with VCFS (aged 8-12 years) and to chronological-age-matched control groups. A first task assessed the integrity of phonological coding in verbal STM by comparing recall for phonologically similar and dissimilar words. Subsequently, the interaction between verbal knowledge and STM capacity was investigated by comparing recall for high- and low-imageability words, for high- and low-frequency words, and for words and non-words. A final task assessed short-term serial order recognition for digit sequences.

RESULTS

When computing the number of items recalled in the word recall tasks, independently of their serial position, only one child presented consistent difficulties. Short-term recall of non-words was normal in each child. Phonological similarity and verbal knowledge influenced STM performance to a similar extent in children with VCFS and controls. On the other hand, when applying a strict serial recall criterion, difficulties with the word and non-word recall tasks were observed in most children. Half of the patients were also impaired in the serial order recognition task.

CONCLUSIONS

Despite mild intellectual disability, it is possible for short-term retention capacities for verbal item information to be at an age-appropriate level in VCFS. However, STM for serial order information could be impaired more specifically.

Identification of a potential bipolar risk haplotype in the gene encoding the winged-helix transcription factor RFX4

The gene encoding the transcription factor RFX4 represents an excellent neurobiological and positional candidate gene for Bipolar disorder due to the potential involvement of RFX4 proteins in the regulation of circadian rhythms and the proximity of the locus to numerous linkage signals on chromosome 12q23. In this study we have sought to identify common variants within the gene, which might confer risk to the disease in our large UK Caucasian sample of Bipolar patients (676 DSMIV Bipolar I probands, 690 controls). RFX4 was screened for sequence variants and the LD block structure across the genomic region determined using 22 biallelic polymorphisms (minor allele frequency >or=0.1). Through analysis of 10 haplotype-tagging markers and using a two-stage approach (subset I: 347 cases, 374 controls; subset II: 329 cases, 316 controls), we identified a haplotype at rs10778502 and ss24735177, which showed nominally significant disease association in our full sample (haplotype-specific P=0.002, global P=0.017; subset I: haplotype-specific P=0.0002, global P=0.0008; subset II: haplotype-specific P=0.572, global P=0.109). Evidence for potential disease association with mutations across the RFX4 region came also from the analysis of the nearby microsatellite D12S2072 (empirical P=0.009 in our full sample). Investigation of RFX4 brain cDNA tagged by rs10778502 provided evidence for significant allelic differences in expression (P<0.001), where some of the variance was accounted for by the genotype at ss24735177. Our findings thus indicate the potential functional relevance of the associated haplotype and now require replication in independent samples.

Hyperinsulinemic hypoglycemia in Beckwith-Wiedemann syndrome due to defects in the function of pancreatic beta-cell adenosine triphosphate-sensitive potassium channels

BACKGROUND

Beckwith-Wiedemann syndrome (BWS) is a congenital overgrowth syndrome that is clinically and genetically heterogeneous. Hyperinsulinemic hypoglycemia occurs in about 50% of children with BWS and, in the majority of infants, it resolves spontaneously. However, in a small group of patients the hypoglycemia can be persistent and may require pancreatectomy. The mechanism of persistent hyperinsulinemic hypoglycemia in this group of patients is unclear.

PATIENTS AND METHODS

Using patch-clamp techniques on pancreatic tissue obtained at the time of surgery, we investigated the electrophysiological properties of ATP-sensitive K(+) (K(ATP)) channels in pancreatic beta-cells in a patient with BWS and severe medically-unresponsive hyperinsulinemic hypoglycemia.

RESULTS

Persistent hyperinsulinism was found to be caused by abnormalities in K(ATP) channels of the pancreatic beta-cell. Immunofluorescence studies using a SUR1 antibody revealed perinuclear pattern of staining in the BWS cells, suggesting a trafficking defect of the SUR1 protein. No mutations were found in the genes ABCC8 and KCNJ11 encoding for the two subunits, SUR1 and KIR6.2, respectively, of the K(ATP) channel. Genetic analysis of this patients BWS showed evidence of mosaic paternal isodisomy.

CONCLUSIONS

In this novel case of BWS with mosaic paternal uniparental disomy for 11p15, persistent hyperinsulinism was due to abnormalities in K(ATP) channels of the pancreatic beta-cell. The mechanism/s by which mosaic paternal uniparental disomy for 11p15 causes a trafficking defect in the SUR1 protein of the K(ATP) channel remains to be elucidated.

A single-nucleotide polymorphism in the RAD51 gene modifies breast cancer risk in BRCA2 carriers, but not in BRCA1 carriers or noncarriers

Variation in the penetrance estimates for BRCA1 and BRCA2 mutation carriers suggests that other genetic polymorphisms may modify the cancer risk in carriers. The RAD51 gene, which participates in homologous recombination double-strand breaks (DSB) repair in the same pathway as the BRCA1 and BRCA2 gene products, is a candidate for such an effect. A single-nucleotide polymorphism (SNP), RAD51-135g → c, in the 5′ untranslated region of the gene has been found to elevate breast cancer (BC) risk among BRCA2 carriers. We genotyped 309 BRCA1/2 mutation carriers, of which 280 were of Ashkenazi origin, 166 noncarrier BC patients and 152 women unaffected with BC (a control group), for the RAD51-135g → c SNP. Risk analyses were conducted using COX proportional hazard models for the BRCA1/2 carriers and simple logistic regression analysis for the noncarrier case–control population. BRCA2 carriers were also studied using logistic regression and Kaplan–Meier survival analyses. The estimated BC hazard ratio (HR) for RAD51-135c carriers adjusted for origin (Ashkenazi vs non-Ashkenazi) was 1.28 (95% CI 0.85–1.90, P=0.23) for BRCA1/2 carriers, and 2.09 (95% CI 1.04–4.18, P=0.04) when the analysis was restricted to BRCA2 carriers. The median BC age was younger in BCRA2-RAD51-135c carriers (45 (95% CI 36–54) vs 52 years (95% CI 48–56), P=0.05). In a logistic regression analysis, the odds ratio (OR) was 5.49 (95% CI 0.5–58.8, P=0.163). In noncarrier BC cases, carrying RAD51-135c was not associated with BC risk (0.97; 95% CI 0.47–2.00). These results indicate significantly elevated risk for BC in carriers of BRCA2 mutations who also carry a RAD51-135c allele. In BRCA1 carriers and noncarriers, no effect for this SNP was found.

Uncontrolled insulin secretion from a childhood pancreatic beta-cell adenoma is not due to the functional loss of ATP-sensitive potassium channels

We report the case of an 8-year-old child who presented with severe hyperinsulinaemic hypoglycaemia due to a pancreatic islet cell adenoma. In vivo, there was no beneficial response to the hyperglycaemia-inducing agent diazoxide and as a consequence the child underwent a subtotal pancreatectomy. In vitro studies of adenomatous beta-cells revealed no operational defects in ATP-sensitive potassium channel activity and appropriate responses to diazoxide. In comparison with patients with focal adenomatous hyperplasia, genetic analysis of the isolated adenoma showed no loss of heterozygosity for chromosome 11p15 and expression of the cyclin-dependent kinase inhibitor p57(kip2). This case illustrates that the excess insulin secretion from an infantile adenoma has an aetiology different from that observed in hyperinsulinism in infancy.

Cortisol and behavior in fragile X syndrome

OBJECTIVE

The purpose of this study was to determine if children with fragile X syndrome, who typically demonstrate a neurobehavioral phenotype that includes social anxiety, withdrawal, and hyper-arousal, have increased levels of cortisol, a hormone associated with stress. The relevance of adrenocortical activity to the fragile X phenotype also was examined.

METHOD

One hundred and nine children with the fragile X full mutation (70 males and 39 females) and their unaffected siblings (51 males and 58 females) completed an in-home evaluation including a cognitive assessment and a structured social challenge task. Multiple samples of salivary cortisol were collected throughout the evaluation day and on two typical non-school days. Measures of the fragile X mental retardation (FMR1) gene, child intelligence, the quality of the home environment, parental psychopathology, and the effectiveness of educational and therapeutic services also were collected. Linear mixed-effects analyses were used to examine differences in cortisol associated with the fragile X diagnosis and gender (fixed effects) and to estimate individual subject and familial variation (random effects) in cortisol hormone levels. Hierarchical multiple regression analyses were conducted to determine whether adrenocortical activity is associated with behavior problems after controlling for significant genetic and environmental factors.

RESULTS

Results showed that children with fragile X, especially males, had higher levels of salivary cortisol on typical days and during the evaluation. Highly significant family effects on salivary cortisol were detected, consistent with previous work documenting genetic and environmental influences on adrenocortical activity. Increased cortisol was significantly associated with behavior problems in boys and girls with fragile X but not in their unaffected siblings.

CONCLUSIONS

These results provide evidence that the function of the hypothalamic-pituitary-adrenal axis may have an independent association with behavioral problems in children with fragile X syndrome.

p57(KIP2) expression in normal islet cells and in hyperinsulinism of infancy

Most cases of hyperinsulinism of infancy (HI) are caused by mutations in either the sulfonylurea receptor-1 (SUR1) or the inward rectifying K(+) channel Kir6.2, two subunits of the beta-cell ATP-sensitive K(+) channel (K(ATP) channel). Histologically, HI can be divided into two major subtypes. The diffuse form is recessively inherited and involves all beta-cells within the pancreas. Focal HI consists of adenomatous hyperplasia within a limited region of the pancreas, and it is caused by somatic loss of heterozygosity (LOH), including maternal Ch11p15-ter in a beta-cell precursor carrying a germ-line mutation in the paternal allele of SUR1 or Kir6.2. Several imprinted genes are located within this chromosomal region, some of which, including p57(KIP2) and IGF-II, have been associated with the regulation of cell proliferation. Using double immunostaining, we examined p57(KIP2) expression in different islet cell types, in control pancreases from different developmental stages (n = 15), and in pancreases from patients with both diffuse (n = 4) and focal HI (n = 9). Using immunofluorescence and computerized image analysis, we quantified IGF-II expression in beta-cells from patients with focal HI (n = 8). Within the pancreas, p57(KIP2) was specifically localized to the endocrine portion. beta-Cells demonstrated the highest frequency of expression (34.9 +/- 2.7%) compared with approximately 1-3% in other cell types. The fraction of beta-cells expressing p57(KIP2) did not vary significantly during development. beta-Cells within the focal lesions did not express p57(KIP2), whereas IGF-II staining inside focal lesions was mildly increased compared with unaffected surrounding tissue. In conclusion, we demonstrate that p57(KIP2) is expressed and is paternally imprinted in human pancreatic beta-cells. Loss of expression in focal HI is caused by LOH and is associated with increased proliferation and increased IGF-II expression. Manipulation of p57(KIP2) expression in beta-cells may provide a mechanism by which proliferation can be modulated, and thus this gene is a potential therapeutic target for reversing the beta-cell failure observed in diabetes.

Recombinant thyroid-stimulating hormone in differentiated thyroid cancer

Recombinant TSH is effective in providing exogenous TSH stimulation for patients with differentiated thyroid cancer on thyroid hormone-suppressive therapy. It allows for detection of thyroid remnant and metastases by radioiodine scan and by serum thyroglobulin determination. The sensitivity and image quality of the WBS are similar after rTSH and after THSH withdrawal in the majority of patients. The equivalent 100% sensitivity of rTSH- and withdrawal-stimulated serum thyroglobulin measurement alone in identifying patients with radioiodine uptake outside the thyroid bed [38] may eventually lead to more extensive use of serum thyroglobulin testing after rTSH, with more selective application of radioiodine WBS [39]. Currently, a phase IV trial is in progress to evaluate the efficacy of rTSH-stimulated thyroglobulin levels as the primary modality for long-term follow-up of low risk thyroid cancer patients. The use of rTSH prevents the morbidity, metabolic impairment and the risk of tumor progression associated with THST withdrawal, because of shorter exposure time to elevated TSH [38]. Furthermore, it decreases the radiation exposure of healthy tissues due to faster iodine clearance in euthyroidism. rTSH is well tolerated, with transient nausea in 10.5% and headache in 7.3% of patients. No antibodies specific to rTSH were documented, even after multiple courses of the drug. Currently, rTSH is suggested for patients who do not respond to hormone withdrawal or cannot tolerate hypothyroidism. For patients with low risk of tumor recurrence, rTSH-stimulated testing may be used at 6-12 months after postoperative I-131 ablation and with a repeat cycle of rTSH one year later, followed by testing every 3-5 years. In high risk patients, one set of negative I-131 scan and thyroglobulin test results after hormone withdrawal are recommended before using rTSH testing, because of a greater sensitivity of the withdrawal scan and because rTSH is not currently approved for subsequent I-131 therapy often indicated in these patients [24]. Subsequently, two cycles of rTSH testing are recommended at 6-12 month intervals, followed by testing every 1-3 years for at least the first decade after initial diagnosis. The cost of this commercially available form of rTSH has been considered a major impediment to its common use; however, this should be weighed against the loss of productivity of working hours related to withdrawal [40]. In the therapeutic setting, rTSH is the only acceptable option in a subgroup of patients with hypopituitarism, ischemic heart disease, a history of "myxedema madness," debilitation due to advanced disease, or inability to elicit TSH elevation due to continued production of thyroxine by thyroid remnant or metastatic tumor [33,38]. In conclusion, recombinant TSH facilitates the management of patients with differentiated thyroid carcinoma. It increases the sensitivity of thyroglobulin testing during thyroid hormone suppression therapy and enables radioiodine uptake for whole-body scan and occasionally for radioiodine therapy, without the need for prolonged THST withdrawal and its associated hypothyroidism, reduced quality of life and risk of tumor progression.

The influence of environmental and genetic factors on behavior problems and autistic symptoms in boys and girls with fragile X syndrome

OBJECTIVE

Fragile X syndrome, caused by mutations in a single gene of the X chromosome (FMR1), is associated with neurobehavioral characteristics including social deficits with peers, social withdrawal, gaze aversion, inattention, hyperactivity, anxiety, depression, and autistic behavior. However, there is considerable variability in the behavioral and psychiatric problems among children with this condition. The purpose of this study was to measure genetic and environmental factors influencing behavior problems and autistic symptoms in children with fragile X syndrome.

DESIGN

We conducted an in-home evaluation of 120 children (80 boys and 40 girls) with the fragile X full mutation and their unaffected siblings, including measurements of the FMR1 protein (FMRP), quality of the home environment, maternal and paternal psychopathology, effectiveness of educational and therapeutic services, and child behavior problems.

RESULTS

Results of multiple regression analyses showed that for boys with fragile X, effectiveness of educational and therapeutic services and parental psychological problems predicted internalizing and externalizing types of problems, while the quality of the home environment predicted autistic behavior. For girls with fragile X, the results emphasized significant effects of FMRP on behavior, in particular social withdrawal and anxious/depressed behavior.

CONCLUSIONS

These findings are among the first to link FMRP expression to behavior. They also emphasize the significance of home- and school-based environmental variables in the neurobehavioral phenotype and help to lay the foundation for studies designed to identify specific interventions for reducing problem behavior in children with fragile X syndrome.

Neurobehavioral phenotype in carriers of the fragile X premutation

There have been contradictory findings in the fragile X (fraX) literature about possible neurocognitive and psychological symptoms due to the fraX premutation (pM). The purpose of the present study was to investigate the relationship between CGG repeat length and neurobehavioral functioning in carriers of the fraX pM. Eighty-five female carriers of the pM with allele sizes ranging from 59-166 were administered a comprehensive IQ test (WAIS-III) and completed a questionnaire designed to measure psychopathology (Symptom Checklist (SCL)-90-R). No relationship between allele size and cognition was identified. A significant negative relationship between allele size and age was found, as well as a positive relationship between allele size and depression. Follow-up analyses separating small and large allele sizes (below and above 100 CGG repeats) indicated that individuals with larger allele sizes scored significantly higher on the Interpersonal Sensitivity and Depression subscales of the SCL-90-R. Despite the limitation of few individuals with high CGG repeat lengths, our findings suggest that females with larger premutated alleles (> or = 100 repeats) display some clinical manifestations of fraX syndrome.

Missense polymorphism in the human carboxypeptidase E gene alters enzymatic activity

Carboxypeptidase E (CPE) is involved in the biosynthesis of peptide hormones and neurotransmitters, including insulin. One of the features of type 2 diabetes mellitus (T2DM) is an elevation in the proinsulin level and/or proinsulin/insulin molar ratio, suggesting that mutations in proinsulin processing enzymes may contribute to the development of T2DM. We scanned CPE for mutations in a collection of Ashkenazi T2DM families and identified five novel single nucleotide polymorphisms (SNPs). An SNP in the 283(rd) codon, c.847C>T, changes arginine to tryptophan (R283W). The residue Arg283 is conserved among CPE orthologs as well as most enzymatically active metallocarboxypeptidases. Of the 272 Ashkenazi T2DM pedigrees screened, we found four families segregating R283W. Within these four families, patients who inherited one copy of this variant had much earlier age of onset for T2DM. The R283W CPE protein cleaves peptide substrates with substantially lower efficiencies and is less stable at elevated temperature. In addition, the R283W CPE variant has a narrower pH optimum and is much less active at pH 6.0-6.5, indicating that the R283W CPE variant would be substantially less active than wild type CPE in the trans-Golgi network and immature secretory vesicles where the enzyme functions in vivo. To summarize, we uncovered a rare non-conservative missense mutation in CPE and demonstrated that the mutant protein has altered enzymatic properties. We predict that this mutant could cause hyperproinsulinism and diabetes in the homozygous state.

CAG and GGC repeat polymorphisms in the androgen receptor gene and breast cancer susceptibility in BRCA1/2 carriers and non-carriers

Variation in the penetrance estimates for BRCA1 and BRCA2 mutations carriers suggests that other genetic polymorphisms may modify the cancer risk in carriers. A previous study has suggested that BRCA1 carriers with longer lengths of the CAG repeat in the androgen receptor (AR) gene are at increased risk of breast cancer (BC). We genotyped 188 BRCA1/2 carriers (122 affected and 66 unaffected with breast cancer), 158 of them of Ashkenazi origin, 166 BC cases without BRCA1/2 mutations and 156 Ashkenazi control individuals aged over 56 for the AR CAG and GGC repeats. In carriers, risk analyses were conducted using a variant of the log-rank test, assuming two sets of risk estimates in carriers: penetrance estimates based on the Breast Cancer Linkage Consortium (BCLC) studies of multiple case families, and lower estimates as suggested by population-based studies. We found no association of the CAG and GGC repeats with BC risk in either BRCA1/2 carriers or in the general population. Assuming BRCA1/2 penetrance estimates appropriate to the Ashkenazi population, the estimated RR per repeat adjusted for ethnic group (Ashkenazi and non-Ashkenazi) was 1.05 (95%CI 0.97-1.17) for BC and 1.00 (95%CI 0.83-1.20) for ovarian cancer (OC) for CAG repeats and 0.96 (95%CI 0.80-1.15) and 0.90 (95%CI 0.60-1.22) respectively for GGC repeats. The corresponding RR estimates for the unselected case-control series were 1.00 (95%CI 0.91-1.10) for the CAG and 1.05 (95%CI 0.90-1.22) for the GGC repeats. The estimated relative risk of BC in carriers associated with > or =28 CAG repeats was 1.08 (95%CI 0.45-2.61). Furthermore, no significant association was found if attention was restricted to the Ashkenazi carriers, or only to BRCA1 or BRCA2 carriers. We conclude that, in contrast to previous observations, if there is any effect of the AR repeat length on BRCA1 penetrance, it is likely to be weak.

Isolation and characterization of the human AKT1 gene, identification of 13 single nucleotide polymorphisms (SNPs), and their lack of association with Type II diabetes

AIMS/HYPOTHESIS

AKT1, a serine/threonine protein kinase, is an important downstream target of the insulin-signalling pathway, with both anti-apoptotic and peripheral metabolic effects. Because impaired insulin signalling is a major hallmark of Type II (non-insulin-dependent) diabetes mellitus, we considered whether the AKT1 gene could be a candidate gene involved in susceptibility of this condition. To test this possibility, we isolated and characterized the human AKT1 gene. We also looked for single nucleotide polymorphisms in the gene and examined their association with Type II diabetes mellitus in the Ashkenazi Jewish population.

METHODS

Human BAC/P1 genomic libraries were screened to isolate the AKT1 gene. To obtain structural information and the sequences of the exon-intron boundaries, BAC/P1 clones were directly sequenced. Identification of single nucleotide polymorphisms was done by polymerase chain reaction of each exon, followed by denaturing high performance liquid chromatography. Six single nucleotide polymorphisms were genotyped in Ashkenazi Jewish patients with Type II diabetes mellitus and in control subjects.

RESULTS

The human AKT1 gene was at least 24.6 kb in length and comprised 14 exons. Altogether 13 putative intragenic single nucleotide polymorphisms, with minor-allele frequencies ranging from 0.011 to 0.354, were identified. The allelic and the genotypic frequencies of 6 single nucleotide polymorphisms were the same in diabetic patients and in control subjects.

CONCLUSION/INTERPRETATION

The results of our studies show that the AKT1 gene is not a major contributor to susceptibility to Type II diabetes mellitus in Ashkenazi Jews.

A genome scan for type 2 diabetes susceptibility loci in a genetically isolated population

A total of 896 individuals of Ashkenazi Jewish descent were ascertained in Israel from 267 multiplex families, including 472 sib-pairs affected with type 2 diabetes. A genome-wide scan with average marker spacing of 9.5 cM revealed five regions on four chromosomes (4q, 8q, 14q, and 20q) that exhibited nominal evidence for linkage (P < 0.05). The highest observed nonparametric linkage Z score was 2.41 (equivalent to a logarithm of odds score of 1.26) at marker D4S1501. A maximal signal, with a Z score of 2.05, was observed on chromosome 20 near marker D20S195, and another on 20p near marker D20S103 (Z 1.80). A single marker on chromosome 8 (D8S593) and two adjacent markers on chromosome 14 (D14S749 and D14S605) also attained evidence of linkage. To explore the hypothesis that the signals on chromosomes 4 and 20 are differentially attributable to variation in BMI or age of onset, an ordered subset analysis was conducted. This analysis revealed that only when the families were ranked by BMI (in increasing order) did a subset attain nominal significance, and only for chromosome 4. The findings reported here lend credence to the hypothesis, now supported by four studies of Caucasian populations and most recently by a combined analysis of 1,852 pedigrees, that a type 2 diabetes susceptibility locus resides on chromosome 20q. This population, because of its unique genetic attributes, may facilitate identification of this and other genes contributing to type 2 diabetes.

Hyperinsulinism of infancy: the regulated release of insulin by KATP channel-independent pathways

Hyperinsulinism of infancy (HI) is a congenital defect in the regulated release of insulin from pancreatic beta-cells. Here we describe stimulus-secretion coupling mechanisms in beta-cells and intact islets of Langerhans isolated from three patients with a novel SUR1 gene defect. 2154+3 A to G SUR1 (GenBank accession number L78207) is the first report of familial HI among nonconsanguineous Caucasians identified in the U.K. Using patch-clamp methodologies, we have shown that this mutation is associated with both a decrease in the number of operational ATP-sensitive K+ channels (KATP channels) in beta-cells and impaired ADP-dependent regulation. There were no apparent defects in the regulation of Ca2+- and voltage-gated K+ channels or delayed rectifier K+ channels. Intact HI beta-cells were spontaneously electrically active and generating Ca2+ action currents that were largely insensitive to diazoxide and somatostatin. As a consequence, when intact HI islets were challenged with glucose and tolbutamide, there was no rise in intracellular free calcium ion concentration ([Ca2+]i) over basal values. Capacitance measurements used to monitor exocytosis in control and HI beta-cells revealed that there were no defects in Ca2+-dependent exocytotic events. Finally, insulin release studies documented that whereas tolbutamide failed to cause insulin secretion as a consequence of impaired [Ca2+]i signaling, glucose readily promoted insulin release. Glucose was also found to augment the actions of protein kinase C- and protein kinase A-dependent agonists in the absence of extracellular Ca2+. These findings document the relationship between SUR1 gene defects and insulin secretion in vivo and in vitro and describe for the first time KATP channel-independent pathways of regulated insulin secretion in diseased human beta-cells.

Dysregulation of insulin secretion in children with congenital hyperinsulinism due to sulfonylurea receptor mutations

Mutations in the high-affinity sulfonylurea receptor (SUR)-1 cause one of the severe recessively inherited diffuse forms of congenital hyperinsulinism or, when associated with loss of heterozygosity, focal adenomatosis. We hypothesized that SUR1 mutations would render the beta-cell insensitive to sulfonylureas and to glucose. Stimulated insulin responses were compared among eight patients with diffuse hyperinsulinism (two mutations), six carrier parents, and ten normal adults. In the patients with diffuse hyperinsulinism, the acute insulin response to intravenous tolbutamide was absent and did not overlap with the responses seen in either adult group. There was positive, albeit significantly blunted, acute insulin response to intravenous dextrose in the patients with diffuse hyperinsulinism. Graded infusions of glucose, to raise and then lower plasma glucose concentrations over 4 h, caused similar rises in blood glucose but lower peak insulin levels in the hyperinsulinemic patients. Loss of acute insulin response to tolbutamide can identify children with diffuse SUR1 defects. The greater response to glucose than to tolbutamide indicates that ATP-sensitive potassium (KATP) channel-independent pathways are involved in glucose-mediated insulin release in patients with diffuse SUR1 defects. The diminished glucose responsiveness suggests that SUR1 mutations and lack of KATP channel activity may contribute to the late development of diabetes in patients with hyperinsulinism independently of subtotal pancreatectomy.

New surgical treatments for macular degeneration

The new surgical techniques described in this article expand the list of new treatments becoming available for people with macular degeneration.

Monilethrix: mutational hotspot in the helix termination motif of the human hair basic keratin 6

Monilethrix is a rare autosomal dominant disease characterized by hair fragility and follicular hyperkeratosis. Mutations in the human basic hair keratins hHb1 and hHb6 have recently been reported in this disease. Twelve families and sporadic cases were clinically diagnosed with monilethrix and were available for the study. The gene segment encoding the helix termination motif region of keratin hHb6 was PCR amplified and sequenced. Mutations were recognized in 6 families. Four families had the previously described mutations, Glu413Lys and Glu413Asp. In 2 unrelated families, a novel mutation, Glu402Lys, was identified. No clear association was found between the severity of the phenotype and the mutation carried. Furthermore, heterozygous members of the same family had variable degrees of hair and skin involvement. Homozygous patients identified in one large consanguineous family were more severely affected. Other genetic or environmental factors may also play a role in monilethrix.

A recessive contiguous gene deletion causing infantile hyperinsulinism, enteropathy and deafness identifies the Usher type 1C gene

Usher syndrome type 1 describes the association of profound, congenital sensorineural deafness, vestibular hypofunction and childhood onset retinitis pigmentosa. It is an autosomal recessive condition and is subdivided on the basis of linkage analysis into types 1A through 1E. Usher type 1C maps to the region containing the genes ABCC8 and KCNJ11 (encoding components of ATP-sensitive K + (KATP) channels), which may be mutated in patients with hyperinsulinism. We identified three individuals from two consanguineous families with severe hyperinsulinism, profound congenital sensorineural deafness, enteropathy and renal tubular dysfunction. The molecular basis of the disorder is a homozygous 122-kb deletion of 11p14-15, which includes part of ABCC8 and overlaps with the locus for Usher syndrome type 1C and DFNB18. The centromeric boundary of this deletion includes part of a gene shown to be mutated in families with type 1C Usher syndrome, and is hence assigned the name USH1C. The pattern of expression of the USH1C protein is consistent with the clinical features exhibited by individuals with the contiguous gene deletion and with isolated Usher type 1C.

Beta-cell proliferation and apoptosis in the developing normal human pancreas and in hyperinsulinism of infancy

Hyperinsulinism of infancy (HI), also known as persistent hyperinsulinemic hypoglycemia of infancy, is a rare genetic disorder that occurs in approximately 1 of 50,000 live births. Histologically, pancreases from HI patients can be divided into 2 major groups. In the first, diffuse HI, beta-cell distribution is similar to that seen in normal neonatal pancreas, whereas in the second, focal HI, there is a discrete region of beta-cell adenomatous hyperplasia. In most patients, the clinical course of the disease suggests a slow progressive loss of beta-cell function. Using double immunostaining, we examined the proportion of beta-cells undergoing proliferation and apoptosis during the development of the normal human pancreas and in pancreases from diffuse and focal HI patients. In the control samples, our findings show a progressive decrease in beta-cell proliferation from 3.2 +/- 0.5% between 17 and 32 weeks of gestation to 0.13 +/- 0.08% after 6 months of age. In contrast, frequency of apoptosis is low (0.6 +/- 0.2%) in weeks 17-32 of gestation, elevated (1.3 +/- 0.3% ) during the perinatal period, and again low (0.08 +/- 0.3%) after 6 months of age. HI beta-cells showed an increased frequency of proliferation, with focal lesions showing particularly high levels. Similarly, the proportion of apoptotic cells was increased in HI, although this reached statistical significance only after 3 months of age. In conclusion, we demonstrated that islet remodeling normally seen in the neonatal period may be primarily due to a wave of beta-cell apoptosis that occurs at that time. In HI, our findings of persistently increased beta-cell proliferation and apoptosis provide a possible mechanism to explain the histologic picture seen in diffuse disease. The slow progressive decrease in insulin secretion seen clinically in these patients suggests that the net effect of these phenomena may be loss of beta-cell mass.

Calcium-stimulated insulin secretion in diffuse and focal forms of congenital hyperinsulinism

OBJECTIVES

To identify infants with hyperinsulinism caused by defects of the beta-cell adenosine triphosphate-dependent potassium channel complex and to distinguish focal and diffuse forms of hyperinsulinism caused by these mutations.

STUDY DESIGN

The acute insulin response to intravenous calcium stimulation (CaAIR) was determined in 9 patients <20 years with diffuse hyperinsulinism caused by defective beta-cell sulfonylurea receptor (SUR1(-/-)), 3 patients with focal congenital hyperinsulinism (6 weeks to 18 months), a 10-year-old with insulinoma, 5 with hyperinsulinism/hyperammonemia syndrome caused by defective glutamate dehydrogenase (6 months to 28 years), 4 SUR1(+/-) heterozygotes with no symptoms, and 9 normal adults. Three infants with congenital focal disease, 1 with diffuse hyperinsulinism, and the child with insulinoma underwent selective pancreatic intra-arterial calcium stimulation with hepatic venous sampling.

RESULTS

Children with diffuse SUR1(-/-) disease and infants with congenital focal hyperinsulinism responded to CaAIR, whereas the normal control group, patients with hyperinsulinism/hyperammonemia syndrome, and SUR1(+/-) carriers did not. Selective arterial calcium stimulation of the pancreas with hepatic venous sampling revealed selective, significant step-ups in insulin secretion that correlated anatomically with the location of solitary lesions confirmed surgically in 2 of 3 infants with congenital focal disease and in the child with insulinoma. Selective arterial calcium stimulation of the pancreas with hepatic venous sampling demonstrated markedly elevated baseline insulin levels throughout the pancreas of the infant with diffuse hyperinsulinism.

CONCLUSIONS

The intravenous CaAIR is a safe and simple test for identifying infants with diffuse SUR1(-/-) hyperinsulinism or with focal congenital hyperinsulinism. Preoperative selective arterial calcium stimulation of the pancreas with hepatic venous sampling can localize focal lesions causing hyperinsulinism in children. The combination of these calcium stimulation tests may help distinguish focal lesions suitable for cure by local surgical resection.

Inhibitors of neovascularization

The use of neovascular inhibitors in the treatment of CNV will no doubt have a profound impact in the future. However, complex issues surround the use of these agents. Careful clinical trials will be necessary to determine the optimal parameters for their use. Furthermore, it must be determined whether these inhibitors will be most efficacious as primary agents or as agents used to augment the efficacy of photoreactive laser treatment or feeder vessel treatment.

Intragenic single nucleotide polymorphism haplotype analysis of SUR1 mutations in familial hyperinsulinism

Familial hyperinsulinism (HI; MIM# 256450) is an autosomal recessive disorder of pancreatic beta-cell function, characterized by inadequate suppression of insulin secretion despite severe recurrent fasting hypoglycemia. Subtotal pancreatectomy is frequently required to prevent permanent neurologic sequelae. The incidence of HI in the Caucasian population is estimated at 1:50,000, however an apparent increased incidence among Ashkenazi Jews and Saudi Arabian Arabs has been reported. A locus for HI was assigned by linkage analyses to human chromosome 11p15.1. The sulfonylurea receptor (MIM# 600509, SUR1) and the potassium channel, inwardly rectifying, subfamily J member 11 (MIM# 600937, KIR6.2) genes, 2 components of the beta-cell K(ATP) channel, are clustered in this chromosomal region, and mutations in these genes have been implicated in HI. We previously demonstrated that two mutations in the SUR1 gene are present on approximately 88% of HI-associated chromosomes in Ashkenazi Jewish patients. Haplotype analysis with microsatellite markers flanking the gene revealed that one mutation (delF1388), reported only in Ashkenazi probands, occurred on two related extended haplotypes. By contrast, the second, more common mutation (3992-9g-->a) was associated with nine different intergenic haplotypes and has been reported in non-Jewish HI patients as well. In this study, we evaluated disease-associated chromosomes from 41 Ashkenazi Jewish and 2 non-Jewish HI patients carrying the 3992-9g-->a mutation by assessing haplotypes defined by nine common single nucleotide polymorphisms (SNPs), six in the SUR1 gene, and three in the KIR6.2 gene. Our results indicate that all 54 chromosomes carrying the 3992-9g-->a mutation in the Jewish patients appear to have originated from one founder mutation, whereas the same mutation on chromosomes from non-Jewish patients originated independently. Furthermore, our findings have implications concerning the HI-associated chromosomes on which no mutation has been identified.

Molecular basis and characterization of the hyperinsulinism/hyperammonemia syndrome: predominance of mutations in exons 11 and 12 of the glutamate dehydrogenase gene. HI/HA Contributing Investigators

Glutamate dehydrogenase (GDH) is allosterically activated by the amino acid leucine to mediate protein stimulation of insulin secretion. Children with the hyperinsulinism/hyperammonemia (HI/HA) syndrome have symptomatic hypoglycemia plus persistent elevations of plasma ammonium. We have reported that HI/HA may be caused by dominant mutations of GDH that lie in a unique allosteric domain that is encoded within GDH exons 11 and 12. To examine the frequency of mutations in this domain, we screened genomic DNA from 48 unrelated cases with the HI/HA syndrome for exon 11 and 12 mutations in GDH. Twenty-five (52%) had mutations in these exons; 74% of the mutations were sporadic. Clinical manifestations included normal birth weight, late onset of hypoglycemia, diazoxide responsiveness, and protein-sensitive hypoglycemia. Enzymatic studies of lymphoblast GDH in seven of the mutations showed that all had reduced sensitivity to inhibition with GTP, consistent with an increase in enzyme activity. Mutations had little or no effect on enzyme responses to positive allosteric effectors, such as ADP or leucine. Based on the three-dimensional structure of GDH, the mutations may function by impairing the binding of an inhibitory GTP to a domain responsible for the allosteric and cooperativity properties of GDH.

Hyperinsulinism of the newborn

Neonatal hyperinsulinism (HI) is a clinical syndrome of pancreatic beta-cell dysfunction characterized by failure to suppress insulin secretion in the presence of hypoglycemia. Although rare, it is the most common cause for persistent hypoglycemia in the newborn period. Treatment can be extremely difficult, and partial pancreatectomy is frequently required to prevent recurrent hypoglycemia and irreversible brain damage. In the last 5 years much has been learned about the pathophysiology of this disease. In most patients, the disease is caused by recessive mutations in either of the 2 functional subunits of the beta-cell KATP channel (SUR1 or Kir6.2). Although in most families, the disease is transmitted as an autosomal recessive trait, a novel form of transmission, resulting in focal involvement of the pancreas has recently been described. Not all patients with HI have mutations in the KATP channel genes. An activating mutation in the "glucose sensor" glucokinase has recently been reported in one family with diazoxide-responsive autosomal dominant hyperinsulinemic hypoglycemia. Also, a new syndrome of hyperinsulinism associated with benign hyperammonemia was recently described and found to be caused by activating mutations in the glutamate dehydrogenase (GDH) gene (GLUD-1). Thus, the clinical syndrome of HI can be caused by mutations in 4 different genes and can be transmitted as either a recessive or a dominant trait. These findings aid in the therapeutic decision-making process and improve the accuracy and precision of genetic counseling. Despite these recent discoveries, however, the metabolic origin of the disease is still unknown in about 50% of cases.

Genetics of neonatal hyperinsulinism

Congenital hyperinsulinism (HI) is a clinically and genetically heterogeneous entity. The clinical heterogeneity is manifested by severity ranging from extremely severe, life threatening disease to very mild clinical symptoms, which may even be difficult to identify. Furthermore, clinical responsiveness to medical and surgical management is extremely variable. Recent discoveries have begun to clarify the molecular aetiology of this disease and thus the mechanisms responsible for this clinical heterogeneity are becoming more clear. Mutations in 4 different genes have been identified in patients with this clinical syndrome. Most cases are caused by mutations in either of the 2 subunits of the beta cell ATP sensitive K(+) channel (K(ATP)), whereas others are caused by mutations in the beta cell enzymes glucokinase and glutamate dehydrogenase. However, for as many as 50% of the cases, no genetic aetiology has yet been determined. The study of the genetics of this disease has provided important new information about beta cell physiology. Although the clinical ramifications of these findings are still limited, in some situations genetic studies might greatly aid in patient management.