A School Intervention Helps Decrease Daily Stress While Enhancing Social Integration in Children

Stress coping is highly relevant during childhood. This study analyses how the participation in a behavioral intervention involving mindfulness-based practices and empathic collaboration activities impact on diurnal cortisol rhythm and social integration in children. In both experimental and waitlist groups, we evaluated before and after the intervention: daily stress, by sampling salivary cortisol at three measurement time-points, and social integration, assessed by a social preference index. Daily average cortisol (DAC) and the area under the curve (AUC) differed when comparing pre-post intervention values in both groups: in the experimental group these measures decreased while in the waitlist group DAC and AUC increased. At the end of the intervention, the experimental group showed an enhancement in the social preference index whereas this parameter diminished in the waitlist group. This kind of behavioral intervention seems to be effective at reducing daily stress and improving social integration in Primary School children.

Impact of Methylmercury and Other Heavy Metals Exposure on Neurocognitive Function in Children Aged 7 Years: Study Protocol of the Follow-up

Background

The extent to which prenatal low-level mercury (Hg) exposure through maternal fish intake and heavy metals exposure affect children’s neurodevelopment is controversial and may appear in the long term. In 2007, a prospective cohort, the Northern Adriatic Cohort II (NAC-II), was established to investigate the association between prenatal Hg exposure from maternal fish consumption and child neurodevelopment. The study enrolled 900 pregnant women, and 632 and 470 children underwent neurodevelopmental evaluation at 18 and 40 months of age, respectively. The NAC-II cohort is a part of the Mediterranean cohort in the “Public health impact of long-term, low-level, mixed element exposure in susceptible population strata” project.

Methods

This protocol describes the follow-up assessment of the effects of prenatal low level Hg and other heavy metals exposure on the developing nervous system of the children born within the NAC-II who reached the age of 7 years. Child diet components are estimated through a Diet Diary. Child hair and urine are collected for determination of Hg level. In addition, levels of other potentially neurotoxic metals, namely Manganese, Cadmium, Lead, Arsenic, and Selenium, are also measured in the same matrices.

Discussion

This protocol extends to the first years of schooling age the evaluation of the neurotoxicant effect of Mercury and of the other heavy metals on children’s neurodevelopment, adjusting for the potential confounders, such as the lifestyles and social economic status of children’s families. Longitudinal analysis of neurodevelopment, assessed in different ages (18 months, 40 months, and 7 years), are performed.

Modulation of genetic associations with serum urate levels by body-mass-index in humans

We tested for interactions between body mass index (BMI) and common genetic variants affecting serum urate levels, genome-wide, in up to 42569 participants. Both stratified genome-wide association (GWAS) analyses, in lean, overweight and obese individuals, and regression-type analyses in a non BMI-stratified overall sample were performed. The former did not uncover any novel locus with a major main effect, but supported modulation of effects for some known and potentially new urate loci. The latter highlighted a SNP at RBFOX3 reaching genome-wide significant level (effect size 0.014, 95% CI 0.008-0.02, Pinter= 2.6 x 10-8). Two top loci in interaction term analyses, RBFOX3 and ERO1LB-EDARADD, also displayed suggestive differences in main effect size between the lean and obese strata. All top ranking loci for urate effect differences between BMI categories were novel and most had small magnitude but opposite direction effects between strata. They include the locus RBMS1-TANK (men, Pdifflean-overweight= 4.7 x 10-8), a region that has been associated with several obesity related traits, and TSPYL5 (men, Pdifflean-overweight= 9.1 x 10-8), regulating adipocytes-produced estradiol. The top-ranking known urate loci was ABCG2, the strongest known gout risk locus, with an effect halved in obese compared to lean men (Pdifflean-obese= 2 x 10-4). Finally, pathway analysis suggested a role for N-glycan biosynthesis as a prominent urate-associated pathway in the lean stratum. These results illustrate a potentially powerful way to monitor changes occurring in obesogenic environment.

The type 2 diabetes associated rs7903146 T allele within TCF7L2 is significantly under-represented in Hereditary Multiple Exostoses: insights into pathogenesis

Hereditary Multiple Exostoses (HME) is an autosomal-dominant disorder characterized by benign cartilage tumors (exostoses) forming near the growth plates, leading to severe health problems. EXT1 and EXT2 are the two genes known to harbor heterozygous loss-of-function mutations that account for the vast majority of the primary genetic component of HME. However, patients present with wide clinical heterogeneity, suggesting that modifier genes play a role in determining severity. Our previous work has pointed to an imbalance of β-catenin signaling being involved in the pathogenesis of osteochondroma formation. TCF7L2 is one of the key 'gate-keeper' TCF family members for Wnt/β-catenin signaling pathway, and TCF7L2 and EXT2 are among the earliest associated loci reported in genome wide appraisals of type 2 diabetes (T2D). Thus we investigated if the key T allele of single nucleotide polymorphism (SNP) rs7903146 within the TCF7L2 locus, which is strongly over-represented among T2D cases, was also associated with HME. We leveraged genotype data available from ongoing GWAS efforts from genomics and orthopedic centers in the US, Canada and Italy. Collectively 213 cases and 1890 controls were analyzed and, surprisingly, the T allele was in fact significantly under-represented in the HME patient group [P = 0.009; odds ratio = 0.737 (95% C.I. 0.587-0.926)]; in addition, the direction of effect was consistent within each individual cohort. Immunohistochemical analyses revealed that TCF7L2 is differentially expressed and distributed in normal human growth plate zones, and exhibits substantial variability in human exostoses in terms of staining intensity and distribution. In summary, the data indicate that there is a putative genetic connection between TCF7L2 and EXT in the context of HME. Given this observation, we suggest that these loci could possibly modulate shared pathways, in particular with respect to β-catenin, and their respective variants interplay to influence HME pathogenesis as well as T2D.

Adult-onset Alexander disease, associated with a mutation in an alternative GFAP transcript, may be phenotypically modulated by a non-neutral HDAC6 variant

Background

We studied a family including two half-siblings, sharing the same mother, affected by slowly progressive, adult-onset neurological syndromes. In spite of the diversity of the clinical features, characterized by a mild movement disorder with cognitive impairment in the elder patient, and severe motor-neuron disease (MND) in her half-brother, the brain Magnetic Resonance Imaging (MRI) features were compatible with adult-onset Alexander’s disease (AOAD), suggesting different expression of the same, genetically determined, condition.

Methods

Since mutations in the alpha isoform of glial fibrillary acidic protein, GFAP-α, the only cause so far known of AOAD, were excluded, we applied exome Next Generation Sequencing (NGS) to identify gene variants, which were then functionally validated by molecular characterization of recombinant and patient-derived cells.

Results

Exome-NGS revealed a mutation in a previously neglected GFAP isoform, GFAP-ϵ, which disrupts the GFAP-associated filamentous cytoskeletal meshwork of astrocytoma cells. To shed light on the different clinical features in the two patients, we sought for variants in other genes. The male patient had a mutation, absent in his half-sister, in X-linked histone deacetylase 6, a candidate MND susceptibility gene.

Conclusions

Exome-NGS is an unbiased approach that not only helps identify new disease genes, but may also contribute to elucidate phenotypic expression.

Genome-wide association analyses identify 18 new loci associated with serum urate concentrations

Elevated serum urate concentrations can cause gout, a prevalent and painful inflammatory arthritis. By combining data from >140,000 individuals of European ancestry within the Global Urate Genetics Consortium (GUGC), we identified and replicated 28 genome-wide significant loci in association with serum urate concentrations (18 new regions in or near TRIM46, INHBB, SFMBT1, TMEM171, VEGFA, BAZ1B, PRKAG2, STC1, HNF4G, A1CF, ATXN2, UBE2Q2, IGF1R, NFAT5, MAF, HLF, ACVR1B-ACVRL1 and B3GNT4). Associations for many of the loci were of similar magnitude in individuals of non-European ancestry. We further characterized these loci for associations with gout, transcript expression and the fractional excretion of urate. Network analyses implicate the inhibins-activins signaling pathways and glucose metabolism in systemic urate control. New candidate genes for serum urate concentration highlight the importance of metabolic control of urate production and excretion, which may have implications for the treatment and prevention of gout.

Genetic characterization of northeastern Italian population isolates in the context of broader European genetic diversity

Population genetic studies on European populations have highlighted Italy as one of genetically most diverse regions. This is possibly due to the country's complex demographic history and large variability in terrain throughout the territory. This is the reason why Italy is enriched for population isolates, Sardinia being the best-known example. As the population isolates have a great potential in disease-causing genetic variants identification, we aimed to genetically characterize a region from northeastern Italy, which is known for isolated communities. Total of 1310 samples, collected from six geographically isolated villages, were genotyped at >145 000 single-nucleotide polymorphism positions. Newly genotyped data were analyzed jointly with the available genome-wide data sets of individuals of European descent, including several population isolates. Despite the linguistic differences and geographical isolation the village populations still show the greatest genetic similarity to other Italian samples. The genetic isolation and small effective population size of the village populations is manifested by higher levels of genomic homozygosity and elevated linkage disequilibrium. These estimates become even more striking when the detected substructure is taken into account. The observed level of genetic isolation in Friuli-Venezia Giulia region is more extreme according to several measures of isolation compared with Sardinians, French Basques and northern Finns, thus proving the status of an isolate.

Genomic profiling by whole-genome single nucleotide polymorphism arrays in Wilms tumor and association with relapse

Despite the excellent survival rate of Wilms tumor (WT) patients, only approximately one-half of children who suffer tumor recurrence reach second durable remission. This underlines the need for novel markers to optimize initial treatment. We investigated 77 tumors using Illumina 370CNV-QUAD genotyping BeadChip arrays and compared their genomic profiles to detect copy number (CN) abnormalities and allelic ratio anomalies associated with the following clinicopathological variables: relapse (yes vs. no), age at diagnosis (≤ 24 months vs. >24 months), and disease stage (low stage, I and II, vs. high stage, III and IV). We found that CN gains at chromosome region 1q21.1-q31.3 were significantly associated with relapse. Additional genetic events, including allelic imbalances at chromosome arms 1p, 1q, 3p, 3q, and 14q were also found to occur at higher frequency in relapsing tumors. Interestingly, allelic imbalances at 1p and 14q also showed a borderline association with higher tumor stages. No genetic events were found to be associated with age at diagnosis. This is the first genome wide analysis with single nucleotide polymorphism (SNP) arrays specifically investigating the role of genetic anomalies in predicting WT relapse on cases prospectively enrolled in the same clinical trial. Our study, besides confirming the role of 1q gains, identified a number of additional candidate genetic markers, warranting further molecular investigations.

New gene functions in megakaryopoiesis and platelet formation

Platelets are the second most abundant cell type in blood and are essential for maintaining haemostasis. Their count and volume are tightly controlled within narrow physiological ranges, but there is only limited understanding of the molecular processes controlling both traits. Here we carried out a high-powered meta-analysis of genome-wide association studies (GWAS) in up to 66,867 individuals of European ancestry, followed by extensive biological and functional assessment. We identified 68 genomic loci reliably associated with platelet count and volume mapping to established and putative novel regulators of megakaryopoiesis and platelet formation. These genes show megakaryocyte-specific gene expression patterns and extensive network connectivity. Using gene silencing in Danio rerio and Drosophila melanogaster, we identified 11 of the genes as novel regulators of blood cell formation. Taken together, our findings advance understanding of novel gene functions controlling fate-determining events during megakaryopoiesis and platelet formation, providing a new example of successful translation of GWAS to function.

Association of a variant in the CHRNA5-A3-B4 gene cluster region to heavy smoking in the Italian population

Large-scale population studies have established that genetic factors contribute to individual differences in smoking behavior. Linkage and genome-wide association studies have shown many chromosomal regions and genes associated with different smoking behaviors. One study was the association of single-nucleotide polymorphisms (SNPs) in the CHRNA5-A3-B4 gene cluster to nicotine addiction. Here, we report a replication of this association in the Italian population represented by three genetically isolated populations. One, the Val Borbera, is a genetic isolate from North-Western Italy; the Cilento population, is located in South-Western Italy; and the Carlantino village is located in South-Eastern Italy. Owing to their position and their isolation, the three populations have a different environment, different history and genetic structure. The variant A of the rs1051730 SNP was significantly associated with smoking quantity in two populations, Val Borbera and Cilento, no association was found in Carlantino population probably because difference in LD pattern in the variant region.

Age-related hearing loss in four Italian genetic isolates: an epidemiological study

The objective of this study was to estimate the prevalence of hearing impairment in four genetically isolated Italian villages (Carlantino, Campora, Gioi-Cardile, and Stoccareddo), 1682 subjects were recruited from all the individuals participating in a multidisciplinary study. They underwent otoscopy and pure-tone audiometry and completed a questionnaire. The audiological data show that the percentage of impaired people increases with age and in particular becomes relevant aged over 40. For this reason we decided to compare the PTA values of individuals aged 40 or older. The PTA values of Stoccareddo and Carlantino are statistically different from PTAs of the other villages. Campora and Gioi-Cardile, both located within the Cilento National Park, have similar middle-low frequency PTA values while some differences are present at high frequencies. Using pedigrees it was possible to calculate the heritability of the trait. For Carlantino and Gioi-Cardile the percentage of the phenotype variation attributable to genetic variation is not significant, while for Campora the heritability value is 0.49 (p = 0.01) suggesting that genetic factors may have an important role.

How does an invasive social wasp deal with changing contextual cues while foraging?

In this study, we explore how an invasive social wasp, Vespula germanica (F.), deals with contextual changes while searching for a food source that is no longer available. Four experiments were conducted to evaluate the effect of different degrees of context modification on wasp behavior. Learning sessions consisted of a variable number of feeding trials during which an individual wasp fed from a landmark array made up of a feeder surrounded by four cylinders of the same color. The food and cylinders were subsequently removed from the training site, and this learned landmark array was modified in such a way that information relating to color and/or location of the resulting feeding arrays varied from that previously learned. The results indicate that the color most recently associated with food is prioritized over a formerly learned color, and this pattern is also maintained when wasps have learned the alternative color during a higher number of feeding experiences. This highlights the high plasticity with which V. germanica responds to unpredictable contextual changes while foraging.

Genetic structure of Europeans: a view from the North-East

Using principal component (PC) analysis, we studied the genetic constitution of 3,112 individuals from Europe as portrayed by more than 270,000 single nucleotide polymorphisms (SNPs) genotyped with the Illumina Infinium platform. In cohorts where the sample size was >100, one hundred randomly chosen samples were used for analysis to minimize the sample size effect, resulting in a total of 1,564 samples. This analysis revealed that the genetic structure of the European population correlates closely with geography. The first two PCs highlight the genetic diversity corresponding to the northwest to southeast gradient and position the populations according to their approximate geographic origin. The resulting genetic map forms a triangular structure with a) Finland, b) the Baltic region, Poland and Western Russia, and c) Italy as its vertexes, and with d) Central- and Western Europe in its centre. Inter- and intra- population genetic differences were quantified by the inflation factor lambda (λ) (ranging from 1.00 to 4.21), fixation index (F_st) (ranging from 0.000 to 0.023), and by the number of markers exhibiting significant allele frequency differences in pair-wise population comparisons. The estimated lambda was used to assess the real diminishing impact to association statistics when two distinct populations are merged directly in an analysis. When the PC analysis was confined to the 1,019 Estonian individuals (0.1% of the Estonian population), a fine structure emerged that correlated with the geography of individual counties. With at least two cohorts available from several countries, genetic substructures were investigated in Czech, Finnish, German, Estonian and Italian populations. Together with previously published data, our results allow the creation of a comprehensive European genetic map that will greatly facilitate inter-population genetic studies including genome wide association studies (GWAS).

Dominant inheritance of a novel integrin beta3 mutation associated with a hereditary macrothrombocytopenia and platelet dysfunction in two Italian families

BACKGROUND

Defects of integrin alpha(IIb)beta(3) are typical of Glanzmann's thrombasthenia, an inherited autosomal recessive bleeding disorder characterized by the failure of platelets to aggregate in response to all physiological agonists, but with no abnormalities in the number or size of platelets. Although large heterogeneity has been described for Glanzmann's thrombasthenia, no family has so far been described as having an autosomal dominant form of this disease.

DESIGN AND METHODS

We describe two Italian families with moderate thrombocytopenia with large platelets, defective platelet function and moderate/severe mucocutaneous bleeding, transmitted as an autosomal dominant trait and associated with a novel integrin beta(3)-gene (ITGB3) mutation.

RESULTS

The characteristics of our families are moderate macrothrombocytopenia and defective platelet function associated with a mild reduction of surface alpha(Ib) beta(3), impaired platelet aggregation to physiological agonists but not to ristocetin, normal clot retraction, reduced fibrinogen binding and expression of activated alpha(IIb)beta(3) upon stimulation, normal platelet adhesion to immobilized fibrinogen but reduced platelet spreading and tyrosine phosphorylation, indicating defective alpha(IIb)beta(3)-mediated outside-in signaling. Molecular analysis revealed a novel mutation of ITGB3 that determines an in-frame deletion producing the loss of amino acids 647-686 of the betaTD ectodomain of integrin beta(3). Haplotype analysis indicated that the two families inherited the mutation from a common ancestral chromosome.

CONCLUSIONS

This novel autosomal dominant macrothrombocytopenia associated with platelet dysfunction raises interesting questions about the role of integrin beta(3), and its betaTD domain, in platelet formation and function.

FASTKD2 nonsense mutation in an infantile mitochondrial encephalomyopathy associated with cytochrome c oxidase deficiency

In two siblings we found a mitochondrial encephalomyopathy, characterized by developmental delay, hemiplegia, convulsions, asymmetrical brain atrophy, and low cytochrome c oxidase (COX) activity in skeletal muscle. The disease locus was identified on chromosome 2 by homozygosity mapping; candidate genes were prioritized for their known or predicted mitochondrial localization and then sequenced in probands and controls. A homozygous nonsense mutation in the KIAA0971 gene segregated with the disease in the proband family. The corresponding protein is known as fas activated serine-threonine kinase domain 2, FASTKD2. Confocal immunofluorescence colocalized a tagged recombinant FASTKD2 protein with mitochondrial markers, and membrane-potential-dependent in vitro mitochondrial import was demonstrated in isolated mitochondria. In staurosporine-induced-apoptosis experiments, decreased nuclear fragmentation was detected in treated mutant versus control fibroblasts. In conclusion, we found a loss-of-function mutation in a gene segregating with a peculiar mitochondrial encephalomyopathy associated with COX deficiency in skeletal muscle. The corresponding protein is localized in the mitochondrial inner compartment. Preliminary data indicate that FASTKD2 plays a role in mitochondrial apoptosis.

Severe infantile encephalomyopathy caused by a mutation in COX6B1, a nucleus-encoded subunit of cytochrome c oxidase

Cytochrome c oxidase (COX) deficiency, one of the most common respiratory-chain defects in humans, has been associated with mutations in either mitochondrial DNA genes or nucleus-encoded proteins that are not part in but promote the biogenesis of COX. Mutations of nucleus-encoded structural subunits were sought for but never found in COX-defective patients, leading to the conjecture that they may be incompatible with extra-uterine survival. We report a disease-associated mutation in one such subunit, COX6B1. Nuclear-encoded COX genes should be reconsidered and included in the diagnostic mutational screening of human disorders related to COX deficiency.

MRX87 family with Aristaless X dup24bp mutation and implication for polyAlanine expansions

Background

Cognitive impairments are heterogeneous conditions, and it is estimated that 10% may be caused by a defect of mental function genes on the X chromosome. One of those genes is Aristaless related homeobox (ARX) encoding a polyA-rich homeobox transcription factor essential for cerebral patterning and its mutations cause different neurologic disorders. We reported on the clinical and genetic analysis of an Italian family with X-linked mental retardation (XLMR) and intra-familial heterogeneity, and provided insight into its molecular defect.

Methods

We carried out on linkage-candidate gene studies in a new MRX family (MRX87). All coding regions and exon-intron boundaries of ARX gene were analysed by direct sequencing.

Results

MRX87 patients had moderate to profound cognition impairment and a combination of minor congenital anomalies. The disease locus, MRX87, was mapped between DXS7104 and DXS1214, placing it in Xp22-p21 interval, a hot spot region for mental handicap. An in frame duplication of 24 bp (ARXdup24) in the second polyAlanine tract (polyA_II) in ARX was identified.

Conclusion

Our study underlines the role of ARXdup24 as a critical mutational site causing mental retardation linked to Xp22. Phenotypic heterogeneity of MRX87 patients represents a new observation relevant to the functional consequences of polyAlanine expansions enriching the puzzling complexity of ARXdup24-linked diseases.

MPV17 encodes an inner mitochondrial membrane protein and is mutated in infantile hepatic mitochondrial DNA depletion

The mitochondrial (mt) DNA depletion syndromes (MDDS) are genetic disorders characterized by a severe, tissue-specific decrease of mtDNA copy number, leading to organ failure. There are two main clinical presentations: myopathic (OMIM 609560) and hepatocerebral (OMIM 251880). Known mutant genes, including TK2, SUCLA2, DGUOK and POLG, account for only a fraction of MDDS cases. We found a new locus for hepatocerebral MDDS on chromosome 2p21-23 and prioritized the genes on this locus using a new integrative genomics strategy. One of the top-scoring candidates was the human ortholog of the mouse kidney disease gene Mpv17. We found disease-segregating mutations in three families with hepatocerebral MDDS and demonstrated that, contrary to the alleged peroxisomal localization of the MPV17 gene product, MPV17 is a mitochondrial inner membrane protein, and its absence or malfunction causes oxidative phosphorylation (OXPHOS) failure and mtDNA depletion, not only in affected individuals but also in Mpv17-/- mice.

Identification of a novel mutation in the myosin VIIA motor domain in a family with autosomal dominant hearing loss (DFNA11)

We ascertained a large Italian family with an autosomal dominant form of non-syndromic sensorineural hearing loss with vestibular involvement. A genome-wide scan found linkage to locus DFNA11. Sequencing of the MYO7A gene in the linked region identified a new missense mutation resulting in an Ala230Val change in the motor domain of the myosin VIIA. Myosin VIIA has already been implicated in several forms of deafness, but this is the third mutation causing a dominant form of deafness, located in the myosin VIIA motor domain in a region never involved in hearing loss until now. A modelled protein structure of myosin VII motor domain provides evidence for a significant functional effect of this missense mutation.

A novel GJA1 mutation causes oculodentodigital dysplasia without syndactyly

Oculodentodigital dysplasia (ODDD) is a rare autosomal dominant pleiotropic disorder, caused by mutations in the Connexin 43 gene (GJA1) [Paznekas et al. (2003): Am J Hum Genet 72:408-418], which is localized to human chromosome 6q22-q23. Here, we describe the identification of a novel heterozygous missense mutation in the GJA1 gene, (H194P) in an Italian family previously reported to be affected by isolated autosomal dominant microphthalmia [Vingolo et al. (1994): J Med Genet 31:721-725]. Careful clinical re-evaluation revealed that this family shows an atypical form of ODDD, characterized by the predominance of the ocular involvement and by the absence of hand and/or foot syndactyly. The mutation affects an amino acid residue localized in the second extracellular domain of the Cx43 protein and highly conserved across evolution. This finding confirms the highly variable phenotypic expression caused by GJA1 mutations.

Behavioral disorder, dementia, ataxia, and rigidity in a large family with TATA box-binding protein mutation

BACKGROUND

Spinocerebellar ataxia type 17 is an autosomal dominant cerebellar ataxia caused by a CAG repeat expansion in the TATA box-binding protein gene. Ataxia is typically the first sign whereas behavioral symptoms occur later.

OBJECTIVE

To characterize the unusual phenotypic expression of a large spinocerebellar ataxia type 17 kindred.

DESIGN

Clinical, neuropathological, and molecular genetic characterization of a 4-generation family with 16 affected patients.

RESULTS

Behavioral symptoms and frontal impairment dominated the early stages preceding ataxia, rigidity, and dystonic movements. Neuropathological examination showed cortical, subcortical, and cerebellar atrophy. Purkinje cell loss and gliosis, pseudohypertrophic degeneration of the inferior olive, marked neuronal loss and gliosis in the caudate nucleus, and in the medial thalamic nuclei were salient features together with neuronal intranuclear inclusions stained with anti-TATA box-binding protein and antipolyglutamine antibodies. The disease was caused by a stable 52 CAG repeat expansion of the TATA box-binding protein gene, although there was apparent variability in the age of onset.

CONCLUSION

The characteristics of this family broaden the clinical picture of spinocerebellar ataxia type 17: initial presenile dementia with behavioral symptoms should be added to ataxia, rigidity, and dystonic movements, which are more commonly encountered.

DNA variants in the human RAB3A gene are not associated with autism

Mutation screening of the RAB3A gene in 47 individuals with autism provided no evidence that DNA variants in this gene are associated with autism. Since Rab3a constitutive knockout mice react to novel stimuli with hyperactivity, a further search for association of RAB3A DNA variants with other neurobehavioral disorders such as attention deficit/hyperactivity disorder appears justified.

Narrowing of the critical region in autosomal recessive spastic paraplegia linked to the SPG5 locus

Hereditary spastic paraplegias are neurodegenerative disorders characterized clinically by progressive spasticity of the lower limbs. They are inherited as autosomal dominant, autosomal recessive, and X-linked traits. Four Italian families with autosomal recessive pure spastic paraplegia are reported. We show evidence of linkage to the SPG5 locus on chromosome 8p and our data reduce the candidate interval for SPG5 to the11-cM interval spanned by D8S285 and D8S544. We also report the search for mutations in five genes located in the region and their exclusion as candidates for SPG5.

A novel autosomal dominant non-syndromic deafness locus (DFNA48) maps to 12q13-q14 in a large Italian family

Non-syndromic hearing loss is the most common sensory disorder in humans; 15%-20% of cases are transmitted as a dominant trait (NSDA) with 40 loci having been mapped and 16 genes having been identified. Here, we report the mapping of a novel NSDA locus, DFNA48, to chromosome 12q13-q14 in a large multigenerational Italian family. A maximum lod score of 3.31 was obtained with marker D12S83, whereas markers D12S347 and D12S1703 defined a region of approximately 18 cM. Positional candidate genes are being screened for deafness-causing mutations.

A new locus (DFNA47) for autosomal dominant non-syndromic inherited hearing loss maps to 9p21-22 in a large Italian family

Hearing loss is the most common sensory disorder in humans, and genetic factors are a major cause. Approximately 15-20% of genetic cases exhibit an autosomal dominant pattern of transmission. So far, 41 autosomal dominant loci have been mapped and 17 genes have been identified. Here we report the mapping of a novel locus for autosomal dominant non-syndromic hearing loss, DFNA47, to chromosome 9p21-22 in a large multigenerational Italian family with progressive hearing impairment. Most affected individuals noticed hearing impairment after their teens with subsequent gradual progression to a moderate-severe loss. There were no obvious vestibular dysfunction and other associated abnormalities. A maximum lod score of 3.14 was obtained with marker D9S157 (at theta=0) after a genome wide search. The study of additional markers allowed us to confirm this region with positive lod scores of 3.58 (at theta=0 from D9S285) and of 3.67 (at theta=0 from D9S162). Recombinants define a region of approximately 9 cM flanked by markers D9S268 and D9S942. Multipoint linkage analysis showed a Lod score of 4.26. Few known genes map to the region, and those possibly related by function to hearing are being screened for disease-causing mutations.

Charcot-Marie-Tooth disease type 2C: a distinct genetic entity. Clinical and molecular characterization of the first European family

Charcot- Marie-Tooth disease type 2 is clinically and genetically heterogeneous. A particular clinical subtype of autosomal dominant Charcot-Marie-Tooth disease type 2, characterized by diaphragm and vocal cord paralysis, is labelled Charcot-Marie-Tooth disease type 2C but no genetic locus has been mapped for this form. We describe the first European family affected by Charcot-Marie-Tooth disease type 2C. Genetic analysis excluded linkage to locus of Charcot-Marie-Tooth disease type 2A, B, D, E and F, and to locus of distal hereditary motor neuronopathy type VII. In this family the disease has high penetrance, variable severity and apparently the most severe limb muscle involvement in the youngest generation. Vocal cord paralysis is unrelated to the degree of muscular weakness and patients with the most severe muscle involvement have absent or minimal respiratory symptoms. Charcot-Marie-Tooth disease type 2C is clinically and genetically different from Charcot-Marie-Tooth disease type 2A, B, D, E and F, and is not allelic with distal hereditary motor neuronopathy type VII.

Conditioned taste aversion as a learning and memory paradigm

Conditioned taste aversion (CTA) is a well established learning and memory paradigm in rats and mice that is considered to be a special form of classical conditioning. Rodents--as well as many other species including man--learn to associate a novel taste (CS) with nausea (US), and as a consequence avoid drinking fluid with this specific taste. In contrast to other types of classical conditioning, even CS-US intervals lasting several hours lead to an aversion to the gustatory CS. With increasing CS-US delay duration, however, the aversion against the CS gradually decreases. Mice differ from rats in their reaction to the CS as well as the US. They tolerate a much higher concentration of saccharin and they do not show any clear signs of nausea when injected with the US. Advantages of this task are its relative independence of motor behavior, well described pathways for the CS and partly the US, and the wealth of available anatomical and pharmacological data implying several brain structures (e.g. parabrachial nucleus, amygdala, insular cortex), neurotransmitters and their receptors (e.g. cholinergic system, NMDA-receptors), and cellular processes (e.g. expression of immediate early genes, Ras-MAP kinase signaling pathway, CREB phosphorilation, protein tyrosine phosphorilation, protein synthesis) in CTA. The CTA paradigm has also been successfully used to phenotype mouse mutants.

X-linked non-specific mental retardation

Non-specific mental retardation is a very common and genetically heterogeneous disorder but, to date, only six genes related to this condition have been identified. Five of these six have been found in the past two years, through positional-cloning efforts of mapped X-linked families. The characteristics of the newly identified genes are providing insights into the molecular mechanisms of mental impairment and the development of cognitive functions.

X chromosome inactivation in carriers of Barth syndrome

Barth syndrome (BTHS) is a rare X-linked recessive disorder characterized by cardiac and skeletal myopathy, neutropenia, and short stature. A gene for BTHS, G4.5, was recently cloned and encodes several novel proteins, named "tafazzins." Unique mutations have been found. No correlation between the location or type of mutation and the phenotype of BTHS has been found. Female carriers of BTHS seem to be healthy. This could be due to a selection against cells that have the mutant allele on the active X chromosome. We therefore analyzed X chromosome inactivation in 16 obligate carriers of BTHS, from six families, using PCR in the androgen-receptor locus. An extremely skewed X-inactivation pattern (>=95:5), not found in 148 female controls, was found in six carriers. The skewed pattern in two carriers from one family was confirmed in DNA from cultured fibroblasts. Five carriers from two families had a skewed pattern (80:20-<95:5), a pattern that was found in only 11 of 148 female controls. Of the 11 carriers with a skewed pattern, the parental origin of the inactive X chromosome was maternal in all seven cases for which this could be determined. In two families, carriers with an extremely skewed pattern and carriers with a random pattern were found. The skewed X inactivation in 11 of 16 carriers is probably the result of a selection against cells with the mutated gene on the active X chromosome. Since BTHS also shows great clinical variation within families, additional factors are likely to influence the expression of the phenotype. Such factors may also influence the selection mechanism in carriers.

Mutations in GDI1 are responsible for X-linked non-specific mental retardation

Rab GDP-dissociation inhibitors (GDI) are evolutionarily conserved proteins that play an essential role in the recycling of Rab GTPases required for vesicular transport through the secretory pathway. We have found mutations in the GDI1 gene (which encodes uGDI) in two families affected with X-linked non-specific mental retardation. One of the mutations caused a non-conservative substitution (L92P) which reduced binding and recycling of RAB3A, the second was a null mutation. Our results show that both functional and developmental alterations in the neuron may account for the severe impairment of learning abilities as a consequence of mutations in GDI1, emphasizing its critical role in development of human intellectual and learning abilities.

The X-linked gene G4.5 is responsible for different infantile dilated cardiomyopathies

Barth syndrome (BTHS) is an X-linked disorder characterized clinically by the associated features of cardiac and skeletal myopathy, short stature, and neutropenia. The clinical manifestations of the disease are, in general, quite variable, but cardiac failure as a consequence of cardiac dilatation and hypertrophy is a constant finding and is the most common cause of death in the first months of life. X-linked cardiomyopathies with clinical manifestations similar to BTHS have been reported, and it has been proposed that they may be allelic. We have recently identified the gene responsible for BTHS, in one of the Xq28 genes, G4.5. In this paper we report the sequence analysis of 11 additional familial cases: 8 were diagnosed as possibly affected with BTHS, and 3 were affected with X-linked dilated cardiomyopathies. Mutations in the G4.5 gene were found in nine of the patients analyzed. The molecular studies have linked together what were formerly considered different conditions and have shown that the G4.5 gene is responsible for BTHS (OMIM 302060), X-linked endocardial fibroelastosis (OMIM 305300), and severe X-linked cardiomyopathy (OMIM 300069). Our results also suggest that very severe phenotypes may be associated with null mutations in the gene, whereas mutations in alternative portions or missense mutations may give a "less severe" phenotype.

X-linked severe mental retardation and a progressive neurological disorder in a Belgian family: clinical and genetic studies

The combination of X-linked mental retardation (XLMR) and neurological disorders occurs in a number of syndromes. Differential diagnosis mostly depends on clinical data and mapping of responsible genes by linkage analysis. We present a Belgian family with severe XLMR and a progressive neurological disorder with ataxia, spasticity and convulsions. Biochemical investigations, neuroimaging and neuropathology were normal. Linkage analysis pointed to region Xq27-28 as the probable locus for the genetic defect. The sequence of the L1CAM cDNA, a possible candidate gene, proved to be normal in the patients. This suggests the presence of a genetic factor on Xq27-28, different from L1CAM, which can lead to severe XLMR and a progressive neurological disorder.

A novel X-linked gene, G4.5. is responsible for Barth syndrome

Barth syndrome is a severe inherited disorder, often fatal in childhood, characterized by cardiac and skeletal myopathy, short stature and neutropenia. The disease has been mapped to a very gene-rich region in distal portion of Xq28. We now report the identification of unique mutations in one of the genes in this region, termed G4.5, expressed at high level in cardiac and skeletal muscle. Different mRNAs can be produced by alternative splicing of the primary G4.5 transcript, encoding novel proteins that differ at the N terminus and in the central region. The mutations introduce stop codons in the open reading frame interrupting translation of most of the putative proteins (which we term 'tafazzins'). Our results suggest that G4.5 is the genetic locus responsible for the Barth syndrome.