Face Processing in Developmental Prosopagnosia: Altered Neural Representations in the Fusiform Face Area

Rationale: Face expertise is a pivotal social skill. Developmental prosopagnosia (DP), i.e., the inability to recognize faces without a history of brain damage, affects about 2% of the general population, and is a renowned model system of the face-processing network. Within this network, the right Fusiform Face Area (FFA), is particularly involved in face identity processing and may therefore be a key element in DP. Neural representations within the FFA have been examined with Representational Similarity Analysis (RSA), a data-analytical framework in which multi-unit measures of brain activity are assessed with correlation analysis. Objectives: Our study intended to scrutinize modifications of FFA-activation during face encoding and maintenance based on RSA. Methods: Thirteen participants with DP (23-70 years) and 12 healthy control subjects (19-62 years) participated in a functional MRI study, including morphological MRI, a functional FFA-localizer and a modified Sternberg paradigm probing face memory encoding and maintenance. Memory maintenance of one, two, or four faces represented low, medium, and high memory load. We examined conventional activation differences in response to working memory load and applied RSA to compute individual correlation-matrices on the voxel level. Group correlation-matrices were compared via Donsker's random walk analysis. Results: On the functional level, increased memory load entailed both a higher absolute FFA-activation level and a higher degree of correlation between activated voxels. Both aspects were deficient in DP. Interestingly, control participants showed a homogeneous degree of correlation for successful trials during the experiment. In DP-participants, correlation levels between FFA-voxels were significantly lower and were less sustained during the experiment. In behavioral terms, DP-participants performed poorer and had longer reaction times in relation to DP-severity. Furthermore, correlation levels were negatively correlated with reaction times for the most demanding high load condition. Conclusion: We suggest that participants with DP fail to generate robust and maintained neural representations in the FFA during face encoding and maintenance, in line with poorer task performance and prolonged reaction times. In DP, alterations of neural coding in the FFA might therefore explain curtailing in working memory and contribute to impaired long-term memory and mental imagery.

Expanding the spectrum of syndromic PPP2R3C-related XY gonadal dysgenesis to XX gonadal dysgenesis

Homozygous variants in PPP2R3C have been reported to cause a syndromic 46,XY complete gonadal dysgenesis phenotype with extragonadal manifestations (GDRM, MIM# 618419) in patients from four unrelated families, whereas heterozygous variants have been linked to reduced fertility with teratozoospermia (SPGF36, MIM# 618420) in male carriers. We present eight patients from four unrelated families of Turkish and Indian descent with three different germline homozygous PPP2R3C variants including a novel in-frame duplication (c.639_647dupTTTCTACTC, p.Ser216_Tyr218dup). All patients exhibit recognizable facial dysmorphisms allowing gestalt diagnosis. In two 46,XX patients with hypergonadotropic hypogonadism and nonvisualized gonads, primary amenorrhea along with absence of secondary sexual characteristics and/or unique facial gestalt led to the diagnosis. 46,XY affected individuals displayed a spectrum of external genital phenotypes from ambiguous genitalia to complete female. We expand the spectrum of syndromic PPP2R3C-related XY gonadal dysgenesis to both XY and XX gonadal dysgenesis. Our findings supported neither ocular nor muscular involvement as major criteria of the syndrome. We also did not encounter infertility problems in the carriers. Since both XX and XY individuals were affected, we hypothesize that PPP2R3C is essential in the early signaling cascades controlling sex determination in humans.

Cutis Tricolor

Cutis tricolor is a skin abnormality consisting in a combination of congenital hyper- and hypopigmented skin lesions (in the form of paired macules, patches, or streaks) in close proximity to each other in a background of normal skin. It is currently regarded as a twin-spotting (mosaic) phenomenon. This phenomenon has been reported so far as a purely cutaneous trait, as a part of a complex malformation phenotype (Ruggieri–Happle syndrome), which includes distinct facial features, cataract, skull and vertebral defects, long bones dysplasia, corpus callosum, cerebellar and white matter anomalies, cavum vergae and holoprosencephaly, and other systemic abnormalities. Cutis tricolor has been also reported as a distinct type with multiple, disseminated smaller skin macules (cutis tricolor parvimaculata) or in association with other skin disturbances (e.g., phacomatosis achromico-melano-marmorata) or in the context of other neurocutaneous phenotypes (e.g., ataxia-telangiectasia and phacomatosis pigmentovascularis) or as a sign of complex malformation phenotypes (e.g., microcephaly and dwarfism). More than 20 studies reporting 40 cases are present in the literature with pure cutaneous or syndromic cutis tricolor phenomena and are analyzed in the present study, confirming and expanding the overall phenotype of cutis tricolor. In particular, (1) the skin abnormalities of the cutis tricolor do not evolve over time; (2) there is a typical facial phenotype with long, elongated face, thick and brushy eyebrows, hypertelorism, deep nasal bridge with large bulbous nose, and anteverted nostrils; (3) the skeletal defects are mild-to-moderate and do not progress or cause relevant orthopedic complications; (4) the neurological/behavioral phenotype does not progress and the paroxysmal events (if present) tend to decrease over time; (5) only three patients developed early onset (treatable) cataracts. Different pathologic hypotheses have been postulated, including, early or late postzygotic mutations involving the same gene loci (in the context of the so-called dydymotic theory): such mechanisms can explain the overall skin, bone, lens, and nervous system phenomena of migration of different streaks of clones in the different tissues.

Next-generation sequencing reveals the mutational landscape of clinically diagnosed Usher syndrome: copy number variations, phenocopies, a predominant target for translational read-through, and PEX26 mutated in Heimler syndrome

Background

Combined retinal degeneration and sensorineural hearing impairment is mostly due to autosomal recessive Usher syndrome (USH1: congenital deafness, early retinitis pigmentosa (RP); USH2: progressive hearing impairment, RP).

Methods

Sanger sequencing and NGS of 112 genes (Usher syndrome, nonsyndromic deafness, overlapping conditions), MLPA, and array‐CGH were conducted in 138 patients clinically diagnosed with Usher syndrome.

Results

A molecular diagnosis was achieved in 97% of both USH1 and USH2 patients, with biallelic mutations in 97% (USH1) and 90% (USH2), respectively. Quantitative readout reliably detected CNVs (confirmed by MLPA or array‐CGH), qualifying targeted NGS as one tool for detecting point mutations and CNVs. CNVs accounted for 10% of identified USH2A alleles, often in trans to seemingly monoallelic point mutations. We demonstrate PTC124‐induced read‐through of the common p.Trp3955* nonsense mutation (13% of detected USH2A alleles), a potential therapy target. Usher gene mutations were found in most patients with atypical Usher syndrome, but the diagnosis was adjusted in case of double homozygosity for mutations in OTOA and NR2E3, genes implicated in isolated deafness and RP. Two patients with additional enamel dysplasia had biallelic PEX26 mutations, for the first time linking this gene to Heimler syndrome.

Conclusion

Targeted NGS not restricted to Usher genes proved beneficial in uncovering conditions mimicking Usher syndrome.

MBTPS2 mutations cause defective regulated intramembrane proteolysis in X-linked osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a collagen-related bone dysplasia. We identified an X-linked recessive form of OI caused by defects in MBTPS2, which encodes site-2 metalloprotease (S2P). MBTPS2 missense mutations in two independent kindreds with moderate/severe OI cause substitutions at highly conserved S2P residues. Mutant S2P has normal stability, but impaired functioning in regulated intramembrane proteolysis (RIP) of OASIS, ATF6 and SREBP transcription factors, consistent with decreased proband secretion of type I collagen. Further, hydroxylation of the collagen lysine residue (K87) critical for crosslinking is reduced in proband bone tissue, consistent with decreased lysyl hydroxylase 1 in proband osteoblasts. Reduced collagen crosslinks presumptively undermine bone strength. Also, proband osteoblasts have broadly defective differentiation. These mutations provide evidence that RIP plays a fundamental role in normal bone development.

Osteogenesis imperfecta (OI) is genetically linked to autosomal dominant or autosomal recessive mutations. Here, Marini et al. describe two families with X-chromosome-linked OI with mutations in MBTPS2 that alter regulated intramembrane proteolysis and subsequent defects in collagen crosslinking and osteoblast function.

Face Perception and Test Reliabilities in Congenital Prosopagnosia in Seven Tests

Congenital prosopagnosia, the innate impairment in recognizing faces, is a very heterogeneous disorder with different phenotypical manifestations. To investigate the nature of prosopagnosia in more detail, we tested 16 prosopagnosics and 21 controls with an extended test battery addressing various aspects of face recognition. Our results show that prosopagnosics exhibited significant impairments in several face recognition tasks: impaired holistic processing (they were tested amongst others with the Cambridge Face Memory Test (CFMT)) as well as reduced processing of configural information of faces. This test battery also revealed some new findings. While controls recognized moving faces better than static faces, prosopagnosics did not exhibit this effect. Furthermore, prosopagnosics had significantly impaired gender recognition—which is shown on a groupwise level for the first time in our study. There was no difference between groups in the automatic extraction of face identity information or in object recognition as tested with the Cambridge Car Memory Test. In addition, a methodological analysis of the tests revealed reduced reliability for holistic face processing tests in prosopagnosics. To our knowledge, this is the first study to show that prosopagnosics showed a significantly reduced reliability coefficient (Cronbach’s alpha) in the CFMT compared to the controls. We suggest that compensatory strategies employed by the prosopagnosics might be the cause for the vast variety of response patterns revealed by the reduced test reliability. This finding raises the question whether classical face tests measure the same perceptual processes in controls and prosopagnosics.

Corrigendum: Do congenital prosopagnosia and the other-race effect affect the same face recognition mechanisms?

[This corrects the article on p. 759 in vol. 8, PMID: 25324757.].

Skeletal dysplasia in a consanguineous clan from the island of Nias/Indonesia is caused by a novel mutation in B3GAT3

We describe a large family with disproportionate short stature and bone dysplasia from Nias in which we observed differences in severity when comparing the phenotypes of affected individuals from two remote branches. We conducted a linkage scan in the more severely affected family branch and determined a critical interval of 4.7 cM on chromosome 11. Sequencing of the primary candidate gene TBX10 did not reveal a disease-causing variant. When performing whole exome sequencing we noticed a homozygous missense variant in B3GAT3, c.419C>T [p.(Pro140Leu)]. B3GAT3 encodes β-1,3-glucuronyltransferase-I (GlcAT-I). GlcAT-I catalyzes an initial step of proteoglycan synthesis and the mutation p. (Pro140Leu) lies within the donor substrate-binding subdomain of the catalytic domain. In contrast to the previously published mutation in B3GAT3, c.830G>A [p.(Arg277Gln)], no heart phenotype could be detected in our family. Functional studies revealed a markedly reduced GlcAT-I activity in lymphoblastoid cells from patients when compared to matched controls. Moreover, relative numbers of glycosaminoglycan (GAG) side chains were decreased in patient cells. We found that Pro140Leu-mutant GlcAT-I cannot efficiently transfer GlcA to the linker region trisaccharide. This failure results in a partial deficiency of both chondroitin sulfate and heparan sulfate chains. Since the phenotype of the Nias patients differs from the Larsen-like syndrome described for patients with mutation p.(Arg277Gln), we suggest mutation B3GAT3:p.(Pro140Leu) to cause a different type of GAG linkeropathy showing no involvement of the heart.

A family at risk: congenital prosopagnosia, poor face recognition and visuoperceptual deficits within one family

Congenital prosopagnosia (CP) describes a severe face processing impairment despite intact early vision and in the absence of overt brain damage. CP is assumed to be present from birth and often transmitted within families. Previous studies reported conflicting findings regarding associated deficits in nonface visuoperceptual tasks. However, diagnostic criteria for CP significantly differed between studies, impeding conclusions on the heterogeneity of the impairment. Following current suggestions for clinical diagnoses of CP, we administered standardized tests for face processing, a self-report questionnaire and general visual processing tests to an extended family (N=28), in which many members reported difficulties with face recognition. This allowed us to assess the degree of heterogeneity of the deficit within a large sample of suspected CPs of similar genetic and environmental background. (a) We found evidence for a severe face processing deficit but intact nonface visuoperceptual skills in three family members - a father and his two sons - who fulfilled conservative criteria for a CP diagnosis on standardized tests and a self-report questionnaire, thus corroborating findings of familial transmissions of CP. (b) Face processing performance of the remaining family members was also significantly below the mean of the general population, suggesting that face processing impairments are transmitted as a continuous trait rather than in a dichotomous all-or-nothing fashion. (c) Self-rating scores of face recognition showed acceptable correlations with standardized tests, suggesting this method as a viable screening procedure for CP diagnoses. (d) Finally, some family members revealed severe impairments in general visual processing and nonface visual memory tasks either in conjunction with face perception deficits or as an isolated impairment. This finding may indicate an elevated risk for more general visuoperceptual deficits in families with prosopagnosic members.

Galactose uncovers face recognition and mental images in congenital prosopagnosia: the first case report

A woman in her early 40s with congenital prosopagnosia and attention deficit hyperactivity disorder observed for the first time sudden and extensive improvement of her face recognition abilities, mental imagery, and sense of navigation after galactose intake. This effect of galactose on prosopagnosia has never been reported before. Even if this effect is restricted to a subform of congenital prosopagnosia, galactose might improve the condition of other prosopagnosics. Congenital prosopagnosia, the inability to recognize other people by their face, has extensive negative impact on everyday life. It has a high prevalence of about 2.5%. Monosaccharides are known to have a positive impact on cognitive performance. Here, we report the case of a prosopagnosic woman for whom the daily intake of 5 g of galactose resulted in a remarkable improvement of her lifelong face blindness, along with improved sense of orientation and more vivid mental imagery. All these improvements vanished after discontinuing galactose intake. The self-reported effects of galactose were wide-ranging and remarkably strong but could not be reproduced for 16 other prosopagnosics tested. Indications about heterogeneity within prosopagnosia have been reported; this could explain the difficulty to find similar effects in other prosopagnosics. Detailed analyses of the effects of galactose in prosopagnosia might give more insight into the effects of galactose on human cognition in general. Galactose is cheap and easy to obtain, therefore, a systematic test of its positive effects on other cases of congenital prosopagnosia may be warranted.

Deficits in long-term recognition memory reveal dissociated subtypes in congenital prosopagnosia

The study investigates long-term recognition memory in congenital prosopagnosia (CP), a lifelong impairment in face identification that is present from birth. Previous investigations of processing deficits in CP have mostly relied on short-term recognition tests to estimate the scope and severity of individual deficits. We firstly report on a controlled test of long-term (one year) recognition memory for faces and objects conducted with a large group of participants with CP. Long-term recognition memory is significantly impaired in eight CP participants (CPs). In all but one case, this deficit was selective to faces and didn't extend to intra-class recognition of object stimuli. In a test of famous face recognition, long-term recognition deficits were less pronounced, even after accounting for differences in media consumption between controls and CPs. Secondly, we combined test results on long-term and short-term recognition of faces and objects, and found a large heterogeneity in severity and scope of individual deficits. Analysis of the observed heterogeneity revealed a dissociation of CP into subtypes with a homogeneous phenotypical profile. Thirdly, we found that among CPs self-assessment of real-life difficulties, based on a standardized questionnaire, and experimentally assessed face recognition deficits are strongly correlated. Our results demonstrate that controlled tests of long-term recognition memory are needed to fully assess face recognition deficits in CP. Based on controlled and comprehensive experimental testing, CP can be dissociated into subtypes with a homogeneous phenotypical profile. The CP subtypes identified align with those found in prosopagnosia caused by cortical lesions; they can be interpreted with respect to a hierarchical neural system for face perception.

Spectrum of skeletal abnormalities in a complex malformation syndrome with "cutis tricolor" (Ruggieri-Happle syndrome)

BACKGROUND

The term cutis tricolor describes the combination of congenital hyper- and hypopigmented skin lesions in close proximity to each other in a background of normal complexion. This phenomenon has been reported: (i) as a purely cutaneous trait; (ii) as a part of a complex malformation syndrome (Ruggieri-Happle syndrome - RHS); (iii) as a distinct type [cutis tricolor parvimaculata]; (iv) in association with other (e.g. vascular) skin disturbances.

OBJECTIVES

To delineate the spectrum of skeletal defects in cutis tricolor.

METHODS

Retrospective and prospective analysis of skeletal surveys in 14 subjects (eight men; six women; aged 2-28 years) with cutis tricolor [4 purely cutaneous trait; 10 syndromic (RHS)].

RESULTS

Bone abnormalities were recorded in 71.4% (10/14) of patients [100% (10/10) of cases with (other-than-skeletal) extra-cutaneous manifestations vs. null (0/4) in cases with purely cutaneous traits] and included overall small skull (n = 6); prognathism (n = 6); 'J'-shaped pituitary fossa (n = 1); absence of atlas posterior arch (n = 3); frontal bossing (n = 6); scoliosis (n = 9) with kyphosis (n = 6) and/or lordosis (n = 6); vertebral (n = 9) and ribs (n = 4) defects. Negative ZFHX1B gene analyses excluded overlaps with Mowat-Wilson syndrome.

CONCLUSIONS

Cutis tricolor may be a marker of underlying skeletal involvement particularly in subjects with a complex syndromic (RHS) phenotype.

Congenital prosopagnosia: multistage anatomical and functional deficits in face processing circuitry

Face recognition is a primary social skill which depends on a distributed neural network. A pronounced face recognition deficit in the absence of any lesion is seen in congenital prosopagnosia. This study investigating 24 congenital prosopagnosic subjects and 25 control subjects aims at elucidating its neural basis with fMRI and voxel-based morphometry. We found a comprehensive behavioral pattern, an impairment in visual recognition for faces and buildings that spared long-term memory for faces with negative valence. Anatomical analysis revealed diminished gray matter density in the bilateral lingual gyrus, the right middle temporal gyrus, and the dorsolateral prefrontal cortex. In most of these areas, gray matter density correlated with memory success. Decreased functional activation was found in the left fusiform gyrus, a crucial area for face processing, and in the dorsolateral prefrontal cortex, whereas activation of the medial prefrontal cortex was enhanced. Hence, our data lend strength to the hypothesis that congenital prosopagnosia is explained by network dysfunction and suggest that anatomic curtailing of visual processing in the lingual gyrus plays a substantial role. The dysfunctional circuitry further encompasses the fusiform gyrus and the dorsolateral prefrontal cortex, which may contribute to their difficulties in long-term memory for complex visual information. Despite their deficits in face identity recognition, processing of emotion related information is preserved and possibly mediated by the medial prefrontal cortex. Congenital prosopagnosia may, therefore, be a blueprint of differential curtailing in networks of visual cognition.

Neurological manifestations in individuals with pure cutaneous or syndromic (Ruggieri-Happle syndrome) phenotypes with "cutis tricolor": a study of 14 cases

BACKGROUND

The term cutis tricolor describes the combination of congenital hyper- and hypo-pigmented skin lesions in close proximity to each other in a background of normal complexion. This phenomenon has been reported so far: (i) as pure cutaneous trait, (ii) as a part of a complex malformation syndrome (Ruggieri-Happle syndrome--RHS), (iii) as a distinct type (cutis tricolor parvimaculata); (iv) in association with other (e. g., vascular) skin disturbances.

AIM

The aim of this study was to define the spectrum of neurological abnormalities in cutis tricolor.

METHODS

A retrospective and prospective 14-year study of clinical, electroencephalographic (EEG), neuroradiological (MRI), cytogenetic and ZFHX1B gene studies of 14 individuals (8 M, 6 F; aged 2-28 years) with cutis tricolor (4 pure cutaneous; 10 syndromic) was undertaken.

RESULTS

Neurological involvement was recorded in 71.4% (10/14) of the patients [100% (10/10) in RHS and null (0/4) in cases with isolated skin manifestations] and included psychomotor delay (n=8), seizures (n=9), EEG abnormalities (n=6), a behavioural phenotype (n=4), non-specific brain abnormalities (n=6). Genetic analyses excluded ZFHX1B mutations and revealed a 19qter deletion (n=1).

CONCLUSIONS

Even though we could not exclude the ascertainment and referral biases, we concluded that cutis tricolor may be a marker of underlying neurological involvement particularly in subjects with a syndromic (RHS) phenotype.

The early time course of compensatory face processing in congenital prosopagnosia

Background

Prosopagnosia is a selective deficit in facial identification which can be either acquired, (e.g., after brain damage), or present from birth (congenital). The face recognition deficit in prosopagnosia is characterized by worse accuracy, longer reaction times, more dispersed gaze behavior and a strong reliance on featural processing.

Methods/Principal Findings

We introduce a conceptual model of an apperceptive/associative type of congenital prosopagnosia where a deficit in holistic processing is compensated by a serial inspection of isolated, informative features. Based on the model proposed we investigated performance differences in different face and shoe identification tasks between a group of 16 participants with congenital prosopagnosia and a group of 36 age-matched controls. Given enough training and unlimited stimulus presentation prosopagnosics achieved normal face identification accuracy evincing longer reaction times. The latter increase was paralleled by an equally-sized increase in stimulus presentation times needed achieve an accuracy of 80%. When the inspection time of stimuli was limited (50ms to 750ms), prosopagnosics only showed worse accuracy but no difference in reaction time. Tested for the ability to generalize from frontal to rotated views, prosopagnosics performed worse than controls across all rotation angles but the magnitude of the deficit didn't change with increasing rotation. All group differences in accuracy, reaction or presentation times were selective to face stimuli and didn't extend to shoes.

Conclusions/Significance

Our study provides a characterization of congenital prosopagnosia in terms of early processing differences. More specifically, compensatory processing in congenital prosopagnosia requires an inspection of faces that is sufficiently long to allow for sequential focusing on informative features. This characterization of dysfunctional processing in prosopagnosia further emphasizes fast and holistic information encoding as two defining characteristics of normal face processing.

Multicolor Karyotyping in Acute Myeloid Leukemia

Cytogenetic data have significantly contributed to our understanding of the heterogeneity of acute myeloid leukemia (AML). In AML, numerous recurrent chromosomal aberrations have been identified, and several of them, e.g. t(8;21)(q22;q22), t(15;17)(q22;q11-12), inv(16)(p13q22), are specific for distinct subgroups. Furthermore, chromosomal aberrations have proved to be of paramount prognostic importance for remission induction and survival. Chromosome analysis using classical cytogenetic banding techniques often fails to completely resolve complex karyotypes and cryptic translocations not identifiable by these techniques have been detected using molecular cytogenetic methods. While fluorescence in situ hybridization (FISH) has become an indispensable tool for screening and follow-up of known aberrations, the techniques of spectral karyotyping (SKY) and multiplex-fluorescence in situ hybridization (M-FISH) allow for the simultaneous visualization of all chromosomes of a metaphase in a single hybridization step, and thereby enable screening for the aberrations present without their prior knowledge. Therefore, with the introduction of these techniques in 1996 the comprehensive analysis of complex karyotypes and the identification of new, hitherto cryptic translocations and, ultimately, the identification of new disease subgroups seemed possible. Since, more than 600 cases of AML and MDS have been analyzed. Herein, we attempt to summarize the data published and discuss what has been achieved towards realization of these goals.

Prevalence of hereditary prosopagnosia (HPA) in Hong Kong Chinese population

Prosopagnosia (PA), or the inability to recognize a familiar person by the face alone, had been considered to be a rare dysfunction mainly acquired by trauma to the brain. Recently we have shown that the congenital form of PA, which was considered to be even rarer, is common in Caucasians, with a prevalence of 2.5%. As these cases were familial we coined the term Hereditary Prosopagnosia (HPA). The present study is the first systematic screening for HPA in a defined population of ethnic Chinese. In 2004-2005, 533 out of around 750 medical students of The University of Hong Kong took part in a questionnaire-based screening. The responses of 133 students indicated that they were likely to be candidates for PA. One hundred twenty agreed for diagnostic interview. Finally we made the clinical diagnosis of PA in 10 subjects. A prevalence of 1.88% (95% CI, 1.05-2.71) is established which is in the same range as in Caucasians. We took a detailed family history of four index prosopagnosic persons and were able to further investigate the families of four probands. Each had other first-degree relatives with the same visual cognitive dysfunction. Thus, as in the Caucasians, regular autosomal dominant inheritance might best explain the segregation pattern.

Genotype-phenotype correlations in Down syndrome identified by array CGH in 30 cases of partial trisomy and partial monosomy chromosome 21

Down syndrome (DS) is one of the most frequent congenital birth defects, and the most common genetic cause of mental retardation. In most cases, DS results from the presence of an extra copy of chromosome 21. DS has a complex phenotype, and a major goal of DS research is to identify genotype-phenotype correlations. Cases of partial trisomy 21 and other HSA21 rearrangements associated with DS features could identify genomic regions associated with specific phenotypes. We have developed a BAC array spanning HSA21q and used array comparative genome hybridization (aCGH) to enable high-resolution mapping of pathogenic partial aneuploidies and unbalanced translocations involving HSA21. We report the identification and mapping of 30 pathogenic chromosomal aberrations of HSA21 consisting of 19 partial trisomies and 11 partial monosomies for different segments of HSA21. The breakpoints have been mapped to within approximately 85 kb. The majority of the breakpoints (26 of 30) for the partial aneuploidies map within a 10-Mb region. Our data argue against a single DS critical region. We identify susceptibility regions for 25 phenotypes for DS and 27 regions for monosomy 21. However, most of these regions are still broad, and more cases are needed to narrow down the phenotypic maps to a reasonable number of candidate genomic elements per phenotype.

First report of prevalence of non-syndromic hereditary prosopagnosia (HPA)

Acquired prosopagnosia (PA) is a rare condition after, for example, a stroke or brain injury. The congenital form of PA is generally considered to be even less common. Beside a few single case reports and anecdotal mentioning of familial cases no data on the epidemiology exists. Following a questionnaire-based screening in local secondary schools and at our medical faculty, candidates suspicious for PA underwent a semi-structured interview followed by examinations of first degree relatives. Among 689 local pupils and medical students of our university we found 17 with congenital PA. This corresponds to a prevalence rate of 2.47% (95% CI 1.31-3.63). The frequency is among the highest known for a monogenic disorder. All those index subjects (n = 14) of the target group who agreed to further examinations of their family members had other first degree relatives with the same cognitive disorder. This study provides epidemiological evidence that congenital PA is a very common cognitive disorder which almost always runs in families. The segregation pattern of this hereditary prosopagnosia (HPA) is fully compatible with autosomal dominant inheritance.

Hereditary Prosopagnosia: the First Case Series

Prosopagnosia is defined as a specific type of visual agnosia characterised by a discernible impairment in the capacity to recognise familiar people by their faces. We present seven family pedigrees with 38 cases in two to four generations of suspected hereditary prosopagnosia, detected using a screening questionnaire. Men and women are impaired and the anomaly is regularly transmitted from generation to generation in all pedigrees studied. Segregation is best explained by a simple autosomal dominant mode of inheritance, suggesting that loss of human face recognition can occur by the mutation of a single gene. Eight of the 38 affected persons were tested on the Warrington Recognition Memory Test for Faces (RMF; Warrington, 1984), famous and family faces tests, learning tests for internal and external facial features and a measure of mental imagery for face and non-face images. As a group, the eight participants scored significantly below an age- and education-matched comparison group on the most relevant test of face recognition; and all were impaired on at least one of the tests. The results provide compelling evidence for significant genetic contribution to face recognition skills and contribute to the promise offered by the emerging field of cognitive neurogenetics.

Hereditary prosopagnosia (HPA): the first report outside the Caucasian population

Prosopagnosia (PA) or face blindness is characterized by a deficiency in identifying familiar faces. Almost all reports are single cases or collections of unrelated patients who acquired prosopagnosia after brain injuries, strokes or atrophy of at least the right occipito-temporal cortex. Until 2001, the inborn form - in the absence of any brain lesions - was described in fewer than 20 probands exclusively of Caucasian origin. We recently found that in the German Caucasian population, congenital prosopagnosia has a very high prevalence of at least 2.5% and that it is genetically determined. It is best described by autosomal-dominant inheritance in the more than 50 families investigated. We therefore introduced the term non-syndromic hereditary PA for the congenital form of a monosymptomatic or isolated PA. This surprisingly high frequency in the Caucasian population prompted us to extend our search to other ethnic groups. We performed a questionnaire-based screening among 198 native Indian students at Banaras Hindu University in Varanasi. In a then selected subset, we found after further detailed diagnostic interviews one Bengali female student with visual agnosia for face recognition only. Several other members of her large family reported the same impairment of face recognition. The segregation pattern of PA in this family is also compatible with autosomal-dominant inheritance.

Gaze behaviour in hereditary prosopagnosia

Prosopagnosia is the inability to recognize someone by the face alone in the absence of sensory or intellectual impairment. In contrast to the acquired form of prosopagnosia we studied the congenital form. Since we could recently show that this form is inherited as a simple monogenic trait we called it hereditary form. To determine whether not only face recognition and neuronal processing but also the perceptual acquisition of facial information is specific to prosopagnosia, we studied the gaze behaviour of four hereditary prosopagnosics in comparison to matched control subjects. This rarely studied form of prosopagnosia ensures that deficits are limited to face recognition. Whereas the control participants focused their gaze on the central facial features, the hereditary prosopagnosics showed a significantly different gaze behaviour. They had a more dispersed gaze and also fixated external facial features. Thus, the face recognition impairment of the hereditary prosopagnosics is reflected in their gaze behaviour.

Mosaic status in lymphocytes of infertile men with or without Klinefelter syndrome

BACKGROUND

Gonosomal aneuploidies such as Klinefelter syndrome (47,XXY) are the most frequent chromosomal aberration in infertile men. Normally the chromosomal status of patients is detected by karyotyping of up to 20 metaphase spreads of lymphocyte nuclei, whereby low grade mosaicism may be overlooked. To test whether Klinefelter patients with 47,XXY karyotype or infertile men with 46,XY karyotype represent gonosomal mosaicisms, we performed meta- and interphase fluorescence in situ hybridization (FISH) on 45 men.

METHODS AND RESULTS

A total of 400 interphase and 40 metaphase lymphocyte nuclei per patient were scored after hybridization with DNA probes specific for chromosomes X and Y, and chromosome 9 as a control. On the basis of conventional karyotype, hormone levels and clinical appearance, patients were subdivided into 18 Klinefelter syndrome patients with 47,XXY (group I), 11 Klinefelter syndrome-like patients with normal karyotype, 46,XY (group II) and six non-Klinefelter-like infertile patients with normal 46,XY karyotype (group III). Ten normal men (group IV) served as controls. Testicular volume in the Klinefelter group I was smaller compared with group II (P = 0.016), group III (P < 0.001) and group IV (P < 0.001). In addition, testicular volumes in group II were lower compared with group III and group IV (P < 0.004). No significant differences between the aneuploidy rate analysed by FISH in interphase nuclei and metaphases were found in either single patients or groups. Patients with Klinefelter syndrome, 47,XXY (group I) or with symptoms similar to those in Klinefelter patients 46,XY (group II) showed a similar aneuploidy rate (group I 7.1 +/- 4.0% and group II 4.6 +/- 3.4%) and two 47,XXY patients with a high prevalence for normal 46,XY lymphocytes had sperm in their ejaculate. However, in general, no correlations between FISH mosaic status and serum hormone parameters, nor with ejaculate parameters were found.

CONCLUSIONS

The results suggest that 47,XXY patients with an increased incidence of XY cells (average of 4.2 +/- 2.3) may have a higher probability of germ cells as we found sperm only in the ejaculate of Klinefelter syndrome patients with mosaic 46,XY cells (6.0 and 7.0%). On the other hand, 46,XY patients with mosaic sex chromosome aneuploidies detected by FISH analysis more often show symptoms of hypogonadism phenotypically resembling Klinefelter syndrome.

Mild phenotype in two unrelated patients with a partial deletion of 21q22.2-q22.3 defined by FISH and molecular studies

We describe two unrelated patients with cytogenetically visible deletions of 21q22.2-q22.3 and mild phenotypes. Both patients presented minor dysmorphic features including thin marfanoid build, facial asymmetry, downward-slanting palpebral fissures, depressed nasal bridge, small nose with bulbous tip, and mild mental retardation (MR). FISH and molecular studies indicated common deleted areas but different breakpoints. In patient 1, the breakpoint was fine mapped to a 5.2 kb interval between exon 5 and exon 8 of the ETS2 gene. The subtelomeric FISH probe was absent on one homologue 21 indicating a terminal deletion spanning approximately 7.9 Mb in size. In patient 2, the proximal breakpoint was determined to be 300-700 kb distal to ETS2, and the distal breakpoint 2.5-0.3 Mb from the 21q telomere, indicating an interstitial deletion sized approximately 4.7-7.3 Mb. The 21q- syndrome is rare and typically associated with a severe phenotype, but different outcomes depending on the size and location of the deleted area have been reported. Our data show that monosomy 21q of the area distal to the ETS2 gene, representing the terminal 7.9 Mb of 21q, may result in mild phenotypes comprising facial anomalies, thin marfanoid build, and mild MR, with or without signs of holoprosencephaly.

Familial aggregation of strong hemispheric language lateralization

The most conspicuous aspect of the neural basis of language is the uneven involvement of the cerebral hemispheres. The familial distribution of variable degrees of left-hemispheric language lateralization was investigated. A significant familial aggregation of strong left-hemispheric language lateralization and a positive association of the degree of language lateralization between parents and their children were found. These data strongly suggest a genetic determination of the degree of language lateralization.

Situs ambiguus in a female fetus with balanced (X;21) translocation – evidence for functional nullisomy of the ZIC3 gene?

The human ZIC3 gene has been mapped to Xq26.2, the visceral heterotaxy locus HTX1, and has been shown to be mutated in X-linked situs ambiguus and/or complex heart defects. We report on a female fetus with situs ambiguus, asplenia and corrected transposition of the great arteries, displaying a (X;21) translocation. The balanced state of the t(X;21)(q26;p13) was verified by FISH on metaphase chromosomes of the fetus using DOP-PCR products of the microdissected der(21) and Xq-subtelomere specific sequences, and by PRINS with beta-satellite specific sequences. Examination with polymorphic markers flanking ZIC3 on DOP-PCR products of the microdissected der(21) chromosome evidenced that the complete copy of the ZIC3 gene was translocated to chromosome 21. Mutations in the fetal and parental ZIC3 genes were excluded by sequencing. Paternal origin of the der(X) and der(21) chromosomes was confirmed by use of polymorphic microsatellite markers from chromosome 21 and from the chromosomal region Xq26, respectively. X chromosome inactivation analysis using a PCR of a polymorphic (CAG)(n) repeat in the first exon of the androgen receptor gene showed a completely skewed X inactivation pattern with the paternal X as the active X chromosome, thus excluding functional disomy of distal Xq. A positional effect caused by the balanced (X;21) translocation may be responsible for functional nullisomy of ZIC3 and thus explain the situs and cardiac abnormalities in the fetus.

PCR-Induced Sequence Alterations Hamper the Typing of Prehistoric Bone Samples for Diagnostic Achondroplasia Mutations

Achondroplasia (ACH) is a skeletal disorder (MIM100800) with an autosomal dominant Mendelian inheritance and complete penetrance. Here we report the screening of ancient bone samples for diagnostic ACH mutations. The diagnostic G-->A transition in the FGFR3 gene at cDNA position 1138 was detected in cloned polymerase chain reaction (PCR) products obtained from the dry mummy of the Semerchet tomb, Egypt (first dynasty, approximately 4,890-5,050 BP [before present]), and from an individual from Kirchheim, Germany (Merovingian period, approximately 1,300-1,500 BP), both of which had short stature. However, these mutations were also reproducibly observed in four ancient control samples from phenotypically healthy individuals (false-positives), rendering the reliable molecular typing of ancient bones for ACH impossible. The treatment of a false-positive DNA extract with uracil N-glycosylase (UNG) to minimize type 2 transitions (G-->A/C-->T) did not reduce the frequency of the false-positive diagnostic ACH mutations. Recently, it was suggested that ancient DNA extracts may induce mutations under PCR. Contemporary human template DNA from a phenotypically healthy individual was therefore spiked with an ancient DNA extract from a cave bear. Again, sequences with the diagnostic G-->A transition in the FGFR3 gene were observed, and it is likely that the false-positive G-->A transitions result from errors introduced during the PCR reaction. Amplifications in the presence of MnCl(2) indicate that position 1138 of the FGFR3 gene is particularly sensitive for mutations. Our data are in line with previously published results on the occurrence of nonrandom mutations in PCR products of contemporary human mitochondrial HVRI template DNA spiked with ancient DNA extracts.

Novel der(1)t(1;19) in two patients with myeloid neoplasias

Cytogenetic studies can be useful in the clinical management of patients with leukemia. They may also give a clue to leukemogenesis and/or pathogenesis. Numerous disease-specific chromosomal aberrations have been and continue to be identified. Translocation (1;19)(q21 through q23;p13.3) involving the long arm of chromosome 1 and the short arm of chromosome 19 is usually associated with acute lymphoblastic leukemia. We found a new translocation involving one virtually identical breakpoint 19p13 and one distinct 1p13 in two cases of myeloid neoplasms. Studies of bone marrow and peripheral blood specimens specified in one of our patients acute myeloid leukemia and in an other myelodysplastic syndrome. Conventional cytogenetics was supplemented by spectral karyotyping (SKY), microdissection, and fluorescence in situ hybridization. Our first case showed a der(1)t(1;19)(p13;p13.1) as the sole chromosomal change. In addition to this translocation, a pericentric inversion within chromosome 10 and with a cryptic t(10;11) were detected by SKY in the second case. Translocation (1;19)(p13;p13.1) may play a role in the leukemogenesis of myeloid diseases.

Recurrent mutations in the COL1A2 gene in patients with osteogenesis imperfecta

A new recurrent point mutation in the COL1A2 gene was found in a patient with type III osteogenesis imperfecta (OI). A G-to-T transversion in nucleotide position 1121 leads to an amino acid substitution Gly238Cys. This is the first report on the most N-terminal cysteine substitution in COL1A2 reported so far. Until now, at this position, only serine substitutions were observed five times in unrelated patients showing a highly variable expression of OI. It is obvious that endogenic and/or exogenic modifiers are involved in this classical autosomal dominant (or rarely recessive) mendelian disorder. An apparent preferential substitution by cysteine and serine residues is discussed with reference to post-transcriptional or post-translational collagen assembly control.

Mirror-symmetric duplicated chromosome 21q with minor proximal deletion, and with neocentromere in a child without the classical Down syndrome phenotype

We report on a mentally retarded child with multiple minor anomalies and an unusually rearranged chromosome 21. This der(21) chromosome has a deletion of 21p and of proximal 21q, whereas the main portion of 21q is duplicated leading to a mirror-symmetric appearance with the mirror axis at the breakpoint. The centromere is only characterized by a secondary constriction (with a centromeric index of a G chromosome) at an unexpected distal position, but fluorescence in situ hybridization (FISH) with either chromosome specific or with all human centromeres alpha satellite DNA shows no cross hybridization. Thus, the marker chromosome represents a further example of an "analphoid marker with neocentromere." Molecular analysis using polymorphic markers on chromosome 21 verified a very small monosomic segment of the proximal long arm of chromosome 21, and additionally trisomy of the remaining distal segment. Although trisomic for almost the entire 21q arm, our patient shows no classical Down syndrome phenotype, but only a few minor anomalies found in trisomy 21 and in monosomy of proximal 21q, respectively.

False-negative findings in chorionic villus sampling. An experimental approach and review of the literature

61 fetuses/newborns who had an aberrant karyotype in amniocentesis (AC) or percutaneous umbilical blood sampling (PUBS) were followed-up by chorionic villus sampling (CVS) at birth or after interruption. The overall rate of discrepancies is surprisingly high. Among 46 cases with a non-mosaic numerical aberration an AC or PUBS three had a discrepant finding in placental tissue. This was also true in one of seven cases with non-mosaic structural aberrations and in three of five cases with mosaic structural aberrations. All three cases with a mosaic numerical aberration in AC or PUBS were not represented by CVS and/or lymphocytes or fibroblasts, demonstrating the general problem of the unpredictable prognostic value of mosaicism. Our data suggest, that in case of prenatal diagnosis by CVS, using a combined procedure of short-term (STC) and long-term culture (LTC), in our sample we would have missed one case of 45,X (1.6 per cent). When relying only on STC another two cases, one with 47, +21 and one with 46,XX,der(22) would not have been recognized (4.9 per cent, n = 3). All other chromosome aberrations would have been detected by STC alone. On the other hand, one case of 45,X was 'nearly missed' because of low-grade mosaicism in AC (45,X[1]/46,XX[19]), whereas in placental tissues and PUBS only 45,X was represented. This study mimics a false-negative rate of about 1:3000 (STC plus LTC) or about 1:1000 (STC alone) for an a priori risk group of two per cent (e.g., advanced maternal age).

"Cutis tricolor": congenital hyper- and hypopigmented macules associated with a sporadic multisystem birth defect: an unusual example of twin spotting?

An uncommon coexistence of circumscribed hyperpigmentation and hypopigmentation, in close proximity to each other, is described in a 17 years old patient with various other cogenital defects, such as dysmorphic facial appearance, severe kyphoscoliosis, delayed motor development, epileptic seizures, and mental retardation. We suggest the combination of hyper- and hypopigmented cutaneous lesions is an example of allelic twin spotting. Because the skin of this patient showed three different degrees of pigmentation the term "cutis tricolor" is proposed.

A case of apparent trisomy 21 without the Down's syndrome phenotype

We describe a case of apparent trisomy 21 that does not fulfill the criteria for the clinical diagnosis of Down's syndrome (DS). Our patient was subjected to karyotype analysis and found to have full, non-mosaic trisomy 21 in both blood lymphocytes and skin fibroblasts, while examination of the term placenta, which was performed earlier in the course of a different study, had shown mosaicism (73%) for trisomy 21. FISH analysis showed no obvious rearrangement of the DS chromosomal region in any of the chromosomes 21. Molecular analysis using polymorphic markers on chromosome 21 verified the existence of trisomy for the entire long arm of the chromosome and showed that the origin of the extra chromosome was maternal and was probably the result of a mitotic error. In contrast with the above, the clinical evaluation using the Jackson checklist of 25 signs failed to establish the diagnosis of DS. We believe that our patient might present mosaicism in other tissues that are not available for analysis and can be regarded as an extreme example in the continuous spectrum of karyotype phenotype associations in mosaic cases.

XX-agonadism in a fetus with multiple dysraphic lesions: a new syndrome

We report on a 19-week-old fetus with a 46,XX karyotype, normal female external genitalia, complete gonadal agenesis, large encephalocele, spina bifida, and omphalocele. We postulate a new syndrome. Hitherto no consistent malformation patterns have been observed in agonadism patients. True agonadism, including even the unusual finding of an XX gonosomal status, is obviously not as rare as suggested.

Characterization of FMR1 promoter elements by in vivo-footprinting analysis

Fragile X syndrome is associated with silencing of the FMR1 gene. We studied the transcriptional regulation, by analysis of the FMR1 promoter region for the presence of in vivo protein/DNA interactions and for cytosine methylation at the single-nucleotide level. Four protein-binding sites were present in the unmethylated promoter of the active FMR1 gene. In the methylated promoter of inactive genes no footprints were detected, and no evidence of active repression was found in the region investigated. We propose that the silencing of FMR1 gene transcription results from a lack of transcription-factor binding.

Characterization of a novel protein kinase C response element in the glucagon gene

To maintain glucose levels in blood within narrow limits, the synthesis and secretion of pancreatic islet hormones are controlled by a variety of neural, hormonal, and metabolic messengers that act through multiple signal transduction pathways. Glucagon gene transcription is stimulated by cyclic AMP and depolarization-induced calcium influx. In this study, the effect of protein kinase C on glucagon gene transcription was investigated. After transient transfection of a glucagon-reporter fusion gene into the glucagon-producing islet cell line alphaTC2, activation of protein kinase C by 12-O-tetradecanoylphorbol-13-acetate (TPA) stimulated glucagon gene transcription. By 5' deletions, 3' deletions, internal deletion, and oligonucleotide cassette insertion, the TPA-responsive element was mapped to the G2 element (from -165 to -200). Like TPA, overexpression of oncogenic Ras (V-12 Ras) stimulated G2-mediated transcription whereas overexpression of a dominant negative Ras mutant (N-17 Ras) blocked the effect of TPA. A mutational analysis of G2 function and nuclear protein binding indicated that protein kinase C and Ras responsiveness is conferred to the glucagon gene by HNF-3beta functionally interacting with a protein that binds to a closely associated site with sequence similarity to binding sites of Ets family proteins. HNF-3beta belongs to the winged-helix family of transcription factors and has been implicated in the control of cell-specific and developmental gene expression. The results of the present study show that the cell lineage-specific transcription factor HNF-3beta is an essential component of a novel protein kinase C response element in the glucagon gene.

X/autosome translocation in three generations ascertained through an infant with trisomy 16p due to failure of spreading of X-inactivation

We report on a reciprocal translocation t(X;16)(q28;p12) detected in a newborn girl with clinical manifestations of partial trisomy 16p. A balanced translocation was found in the mother and in the maternal grandmother. Replication studies on lymphocytes and fibroblasts showed nonrandom X-inactivation in both the patient and her mother. In the mother, the derivative X (der(X)) was active, whereas the normal X was late replicating. In contrast, in the patient the der(X) was late replicating, and there was no spreading of X-inactivation onto the autosomal segment, thus giving an explanation for the full clinical picture of partial trisomy 16p.

Agonadism in two sisters with XY gonosomal constitution, mental retardation, short stature, severely retarded bone age, and multiple extragenital malformations: a new autosomal recessive syndrome

We report on 12- and 14-year old sisters with a 46, XY chromosome constitution, normal female external genitalia, and absence of gonadal tissue. Except for omphalocele, right renal agenesis and malrotation of the colon in the elder sister, the internal organs were normal. Both were mentally retarded, of short stature, and had extremely retarded bone age. In addition, they had an almost identical pattern of minor anomalies: peculiar face, hypodontia, short neck, inverted nipples, thoracolumbar scoliosis, "dysplastic" hips, partial clino-/syndactyly of toes. The occurrence of a basically similar set of malformations in two sisters and the first cousin consanguinity of the parents suggests autosomal recessive inheritance. The conserved region of the SRY gene ([high mobility group] HMG box) was sequenced in the elder sib and was normal. No consistent malformations are observed at present in agonadal patients. This supports the idea that several autosomal genes have the potential of influencing the sequence of events of sex determination.