Microarray based analysis of 3p25-p26 deletions (3p- syndrome)

Prenatal diagnosis of familial 3p26.3p25.3 deletion in a pregnancy associated with a favorable fetal outcome and asymptomatic carrier parent and family members in three generations

OBJECTIVE

We present prenatal diagnosis of familial 3p26.3p25.3 deletion in a pregnancy associated with a favorable fetal outcome and asymptomatic carrier parent and family members in three generations.

CASE REPORT

A 35-year-old, gravida 2, para 1, woman underwent amniocentesis at 17 weeks of gestation because of advanced maternal age and the carrier of distal 3p deletion. She was phenotypically normal, and there was no family history of congenital anomalies. Amniocentesis revealed a karyotype of 46,XY,del(3)(p26.1). Repeat amniocentesis at 21 weeks of gestation revealed a karyotype of 46,XY,del(3)(p25.3). Simultaneous array comparative genomic hybridization (aCGH) analysis on the DNA extracted from uncultured amniocytes showed the result of arr 3p26.3p25.3 (117,735-8,709,972) × 1.0 [GRCh37 (hg19)] with an 8.59-Mb deletion of 3p26.3p25.3 encompassing 14 OMIM genes of CHL1, CNTN6, CNTN4, IL5RA, TRNT1, CRBN, SETMAR, SUMF1, ITPR1, BHLHE40, ARL8B, GRM7, LMCD1 and SSUH2. Cytogenetic analysis of parental bloods revealed a karyotype of 46,XX,del (3) (p25.3) in the mother and 46,XY in the father. The woman's 69-year-old mother and her 2-year-old elder son carried the same aberrant chromosome of 3p25.3→p26.3 deletion by conventional cytogenetic analysis but manifested no phenotypic abnormality. aCGH analysis of the peripheral bloods showed that the woman's mother and her elder son had the same 8.59-Mb deletion of 3p26.3p25.3. The woman was advised to continue the pregnancy. At 39 weeks of gestation, a 3040-g healthy male baby was delivered. When follow-up at age 2½ years, the neonate was normal in development and showed no apparent phenotypic abnormality.

CONCLUSION

Distal 3p deletion of 3p26.3p25.3 involving the OMIM genes from CHL1 to SSUH2 can be associated with no apparent phenotypic abnormality.

Neurobehavioral characteristics of mice with SETD5 mutations as models of IDD23 and KBG syndromes

Genomic analysis has revealed that the genes for various chromatin regulators are mutated in many individuals with neurodevelopmental disorders (NDDs), emphasizing the important role of chromatin regulation in nervous system development and function. Chromatin regulation is mediated by writers, readers, and erasers of histone and DNA modifications, with such proteins being defined by specific domains. One of these domains is the SET domain, which is present in enzymes that catalyze histone methylation. Heterozygous loss-of-function mutations of the SETD5 (SET domain containing 5) gene have been identified in individuals with an NDD designated IDD23 (intellectual developmental disorder, autosomal dominant 23). KBG syndrome (named after the initials of the last names of the first three families identified with the condition) is characterized by features that either overlap with or are distinct from those of IDD23 and was initially thought to be caused only by mutations in the ANKRD11 (ankyrin repeat domain containing 11) gene. However, recent studies have identified SETD5 mutations in some KBG syndrome patients without ANKRD11 mutations. Here we summarize the neurobehavioral characterization of Setd5 ^+/- mice performed by four independent research groups, compare IDD23 and KBG phenotypes, and address the utility and future development of mouse models for elucidation of the mechanisms underlying NDD pathogenesis, with a focus on SETD5 and its related proteins.

Novel duplication of the cell adhesion molecule L1-like gene in an individual with cognitive impairment, tall stature, and obesity: A case report

The gene that codes for the close homolog of L1 (CHL1 gene) is located in the 3p26.3 cytogenetic band in the distal portion of the 3p chromosome. This gene is highly expressed in the central nervous system and plays an important role in brain formation and plasticity. Complete or partial CHL 1 gene-deficient mice have demonstrated neurocognitive deficits. In humans, mutations of the CHL 1 gene are infrequent with most mutations described in the literature as deletions. This case report describes an individual with a duplication in the CHL 1 and a presentation consistent with a syndromic form of neurocognitive impairment. To the best of our knowledge, this mutation has not been previously described in the literature.

Partial Trisomy 13q/Monosomy 3p Resulting from a Paternal Reciprocal 3p;13q Translocation in a Boy with Facial Dysmorphism and Hypertrophic Cardiomyopathy

Individuals with 3p deletion show a great clinical variability. Apparently, a 1.5-Mb terminal deletion, including the CRBN and CNTN4 genes, is sufficient to cause this syndrome. Partial trisomy 13q is a rare chromosomal abnormality with a variable phenotypic expression, but in most cases, patients have a phenotype resembling complete trisomy 13. The aim of the present study is to describe a 9-month-old Mexican male patient with 3p deletion/13q duplication and a novel clinical finding. He presented with facial dysmorphism and multiple congenital alterations. Echocardiogram revealed cardiac insufficiency with hypertrophic cardiomyopathy and pulmonary hypertension, not previously reported. Karyotype from the patient and his father were 46,XY,add(3)(p26) and 46,XY,t(3;13), respectively. Microarray assay of the proband exhibited an approximately 2.6-Mb loss at terminal 3p26.3 and a 27.7-Mb gain of the long arm in terminal chromosome 13 at q31.1q34. A chromosomal imbalance with a partial trisomy 13q31.1q34 and monosomy 3p26.3 of paternal origin were detected. Microarray assay of both parents were normal. The proband has a cardiomyopathy not previously reported. These data enrich the spectrum of clinical manifestations in 3p deletion/3q duplication chromosomopathy.

Fetal Cystic Hygroma Associated with Terminal 2p25.1 Duplication and Terminal 3p25.3 Deletion: Cytogenetic, Fluorescent in Situ Hybridization and Microarray Familial Characterization of Two Different Chromosomal Structural Rearrangements

We report a prenatally diagnosed case of partial trisomy 2p and partial monosomy 3p, resulting from unbalanced translocation (2;3)(p25.1;p25.3) of paternal origin. Parents were non consanguineous Caucasians, with familial history of recurrent miscarriages on the father’s side. Detailed sonographic examination of the fetus showed a septated cystic hygroma measuring 6 mm at 13 weeks’ gestation. Karyotyping and fluorescent in situ hybridization (FISH) analysis of cultured amniotic fluid cells revealed an unbalanced translocation der(3)t(2;3)(p25.1; p25.3) and apparently balanced inv(3)(p13p25.3) in a fetus. Parental cytogenetic evaluation using karyotyping and FISH analysis showed the presence of both a balanced translocation and a paracentric inversion in father t(2;3) (p25.1;p25.3) inv(3)(p13p25.3). Microarray analysis showed a 11.6 Mb deletion at 3p26.3-p25.3 and duplication of 10.5 Mb at the 2p25.3-p25 region. The duplicated region at 2p25.1p25.3 contains 45 different genes, where 12 are reported as OMIM morbid genes with different phenotypical implications. The deleted region at 3p26.3-p25.3 contains 65 genes, out of which 27 are OMIM genes.

Three of these (CNTN4, SETD5 and VHL) were curated by Clingene Dosage Gene Map and were given a high haplo-insufficiency score. Genes affected by the unbalanced translocation could have contributed to some specific phenotypic changes of the fetus in late pregnancy. The application of different cytogenetic methods was essential in our case, allowing the detection of different types of structural chromosomal aberrations and more thorough genetic counseling for future pregnancies.

Cell Adhesion Molecules Involved in Neurodevelopmental Pathways Implicated in 3p-Deletion Syndrome and Autism Spectrum Disorder

Autism spectrum disorder (ASD) is characterized by impaired social interaction, language delay and repetitive or restrictive behaviors. With increasing prevalence, ASD is currently estimated to affect 0.5–2.0% of the global population. However, its etiology remains unclear due to high genetic and phenotypic heterogeneity. Copy number variations (CNVs) are implicated in several forms of syndromic ASD and have been demonstrated to contribute toward ASD development by altering gene dosage and expression. Increasing evidence points toward the p-arm of chromosome 3 (chromosome 3p) as an ASD risk locus. Deletions occurring at chromosome 3p result in 3p-deletion syndrome (Del3p), a rare genetic disorder characterized by developmental delay, intellectual disability, facial dysmorphisms and often, ASD or ASD-associated behaviors. Therefore, we hypothesize that overlapping molecular mechanisms underlie the pathogenesis of Del3p and ASD. To investigate which genes encoded in chromosome 3p could contribute toward Del3p and ASD, we performed a comprehensive literature review and collated reports investigating the phenotypes of individuals with chromosome 3p CNVs. We observe that high frequencies of CNVs occur in the 3p26.3 region, the terminal cytoband of chromosome 3p. This suggests that CNVs disrupting genes encoded within the 3p26.3 region are likely to contribute toward the neurodevelopmental phenotypes observed in individuals affected by Del3p. The 3p26.3 region contains three consecutive genes encoding closely related neuronal immunoglobulin cell adhesion molecules (IgCAMs): Close Homolog of L1 (CHL1), Contactin-6 (CNTN6), and Contactin-4 (CNTN4). CNVs disrupting these neuronal IgCAMs may contribute toward ASD phenotypes as they have been associated with key roles in neurodevelopment. CHL1, CNTN6, and CNTN4 have been observed to promote neurogenesis and neuronal survival, and regulate neuritogenesis and synaptic function. Furthermore, there is evidence that these neuronal IgCAMs possess overlapping interactomes and participate in common signaling pathways regulating axon guidance. Notably, mouse models deficient for these neuronal IgCAMs do not display strong deficits in axonal migration or behavioral phenotypes, which is in contrast to the pronounced defects in neuritogenesis and axon guidance observed in vitro. This suggests that when CHL1, CNTN6, or CNTN4 function is disrupted by CNVs, other neuronal IgCAMs may suppress behavioral phenotypes by compensating for the loss of function.

Case Report: A Case Report and Literature Review of 3p Deletion Syndrome

Objective: The aim of the present study is to explore the clinical and genetic characteristics of 3p deletion syndrome to improve clinicians' understanding of the disease. Methods: The clinical manifestations, process of diagnosis and treatment, and genetic characteristics of an individual case of 3p deletion syndrome were analyzed. CNKI, Wanfang Data, and the Biomedical Literature Database (PubMed) were searched. The search time limit, using "3p deletion syndrome" and "BRPF1" as keywords, was from the creation of the database up to June 2020. Related data were reviewed. Results: The proband was a male child with general developmental and intellectual disabilities, special facial features and congenital heart disease. The child was the parents' first pregnancy and first born. Gene microarray analysis showed a 10.095 Mb deletion in the 3p26.3-p25.3 region, resulting in a heterozygous mutation of the BRPF1 gene; thus, the patient was diagnosed with 3p deletion syndrome. At the time of diagnosis, the child was 1 year of age and was responding to comprehensive rehabilitation training. A total of 29 well-documented cases were found in the literature, of which 19 cases had an onset within 1 year of birth, and mainly manifested with mental and motor development disabilities and abnormal facial features, with different gene deletions, depending on the size and location of the 3p deletion. Conclusion: The genetic test results of the child in this study indicated a heterozygous deletion of the BRPF1 gene on the short arm of chromosome 3, which was a unique feature of this study, since it was rarely mentioned in other reports of 3p deletion syndrome. The clinical phenotype of this syndrome is complex as it can include intellectual and motor development backwardness, low muscle tone, certain abnormal facial features (low hairline, bilateral ptosis, widely spaced eyes, a forward nose, left ear auricle deformity, a high-arched palate, a small jaw), and the deformation of systems such as the gastrointestinal tract and the urinary tract malformation or symptoms of epilepsy. As clinical manifestations can be relatively mild, the syndrome is easy to miss or misdiagnose. Clinical workers need to be aware of this disease when they find that children have special features, such as stunted growth, low muscle tone or ptosis, and it needs to be diagnosed through genetic testing. Most children are able to develop certain social skills after rehabilitation treatment.

Genetic Basis of Human Congenital Heart Disease

Congenital heart disease (CHD) is the most common major congenital anomaly with an incidence of ∼1% of live births and is a significant cause of birth defect-related mortality. The genetic mechanisms underlying the development of CHD are complex and remain incompletely understood. Known genetic causes include all classes of genetic variation including chromosomal aneuploidies, copy number variants, and rare and common single-nucleotide variants, which can be either de novo or inherited. Among patients with CHD, ∼8%-12% have a chromosomal abnormality or aneuploidy, between 3% and 25% have a copy number variation, and 3%-5% have a single-gene defect in an established CHD gene with higher likelihood of identifying a genetic cause in patients with nonisolated CHD. These genetic variants disrupt or alter genes that play an important role in normal cardiac development and in some cases have pleiotropic effects on other organs. This work reviews some of the most common genetic causes of CHD as well as what is currently known about the underlying mechanisms.

A novel mutation in a common pathogenic gene (SETD5) associated with intellectual disability: A case report

Intellectual disability (ID) is a non-specific phenotype present in a genetically heterogeneous group of disorders. The genetic cause of ID remains elusive in the majority of patients due to this extreme heterogeneity. Whole exome sequencing technology has been applied to identify pathogenic gene variants responsible for ID. The present report described a 1.7-year-old female patient who had severe ID with the specific features of delayed motor development, language disorders and abnormal facial features. Exome analysis identified a novel pathogenic variant of the SETD5 gene [c.2025_2026delAG (p.Gly676Valfs*2)]. The variant was a frameshift mutation, causing termination of the protein in advance. These findings indicated that this mutation of the SETD5 gene may be a genetic cause for ID. The present study aimed to provide a meaningful exploration of ID and the identification of clinical core genetic pedigrees.

Importance of patient selection criteria in determining diagnostic copy number variations in patients with multiple congenital anomaly/mental retardation

Background

Etiology of developmental delay/intellectual disability is very heterogeneous. In recent years, genetic causes have been defined through the use of chromosomal microarray analysis as a first step genetic test.

Results

Samples from 30 patients with multiple congenital anomaly and/or mental retardation were analyzed with array comparative genomic hybridization in the context of this study. Before this analysis, karyotyping, subtelomeric fluorescence in situ hybridization and additionally fragment analysis for fragile X in males, had been routinely made all of which were reported to be normal. The purpose of our study was to determine the copy number variations as well as to investigate methods to increase diagnostic yield of array comparative genomic hybridization and forming a suitable flow chart decision pipeline for test indication especially for developing countries. Genomic changes were identified at a rate of about 27% in our series. Although this ratio is higher than the literature data, it could be due to the patient selection criteria.

Conclusion

Chromosomal microarray analysis is not easily utilized for all patients because of its high-cost. Thus, for increasing cost-effectiveness, it may be used step by step for defined targets. Along with discussing the patients with copy number variations relevant with the phenotype, we suggest a flow chart for selection of diagnostic test with the highest diagnostic rate and the lowest expenditure which is quite important for developing countries.

Genome-wide association analysis reveals KCTD12 and miR-383-binding genes in the background of rumination

Ruminative response style is a passive and repetitive way of responding to stress, associated with several disorders. Although twin and candidate gene studies have proven the genetic underpinnings of rumination, no genome-wide association study (GWAS) has been conducted yet. We performed a GWAS on ruminative response style and its two subtypes, brooding and reflection, among 1758 European adults recruited in the general population of Budapest, Hungary, and Manchester, United Kingdom. We evaluated single-nucleotide polymorphism (SNP)-based, gene-based and gene set-based tests, together with inferences on genes regulated by our most significant SNPs. While no genome-wide significant hit emerged at the SNP level, the association of rumination survived correction for multiple testing with KCTD12 at the gene level, and with the set of genes binding miR-383 at the gene set level. SNP-level results were concordant between the Budapest and Manchester subsamples for all three rumination phenotypes. SNP-level results and their links to brain expression levels based on external databases supported the role of KCTD12, SRGAP3, and SETD5 in rumination, CDH12 in brooding, and DPYSL5, MAPRE3, KCNK3, ATXN7L3B, and TPH2 in reflection, among others. The relatively low sample size is a limitation of our study. Results of the first GWAS on rumination identified genes previously implicated in psychiatric disorders underscoring the transdiagnostic nature of rumination, and pointed to the possible role of the dorsolateral prefrontal cortex, hippocampus, and cerebellum in this cognitive process.

Genetic variations on SETD5 underlying autistic conditions

The prevalence of autism spectrum disorders (ASD) and the number of identified ASD-related genes have increased in recent years. The SETD5 gene encodes a SET-containing-domain 5 protein, a likely reader enzyme. Genetic evidences suggest that SETD5 malfunction contributes to ASD phenotype, such as on intellectual disability (ID) and facial dysmorphism. In this review, we mapped the clinical phenotypes of individuals carrying mutations on the SETD5 gene that are associated with ASD and other chromatinopathies (mutation in epigenetic modifiers that leads to the development of neurodevelopmental disorders such as ASD). After a detailed systematic literature review and analysis of public disease-related databank, we found so far 42 individuals carrying mutations on the SETD5 gene, with 23.8% presenting autistic-like features. Furthermore, most of mutations occurred between positions 9,480,000-9,500,000 bp on chromosome 3 (3p25.3) at the SETD5 gene locus. In all males, mutations in SETD5 presented high penetrance, while in females the clinical phenotype seems more variable with two reported cases showing normal female carriers and not presenting ASD or any ID-like symptoms. At the molecular level, SETD5 interacts with proteins of PAF1C and N-CoR complexes, leading to a possible involvement with chromatin modification pathway, which plays important roles for brain development. Together, we propose that mutations on the SETD5 gene could lead to a new syndromic condition in males, which is linked to 3p25 syndrome, and can leads to ASD-related intellectual disability and facial dysmorphism. © 2018 Wiley Periodicals, Inc. Develop Neurobiol 78: 500-518, 2018.

Mind the (sr)GAP - roles of Slit-Robo GAPs in neurons, brains and beyond

The Slit-Robo GTPase-activating proteins (srGAPs) were first identified as potential Slit-Robo effectors that influence growth cone guidance. Given their N-terminal F-BAR, central GAP and C-terminal SH3 domains, srGAPs have the potential to affect membrane dynamics, Rho family GTPase activity and other binding partners. Recent research has clarified how srGAP family members act in distinct ways at the cell membrane, and has expanded our understanding of the roles of srGAPs in neuronal and non-neuronal cells. Gene duplication of the human-specific paralog of srGAP2 has resulted in srGAP2 family proteins that may have increased the density of dendritic spines and promoted neoteny of the human brain during crucial periods of human evolution, underscoring the importance of srGAPs in the unique sculpting of the human brain. Importantly, srGAPs also play roles outside of the nervous system, including during contact inhibition of cell movement and in establishing and maintaining cell adhesions in epithelia. Changes in srGAP expression may contribute to neurodevelopmental disorders, cancer metastasis and inflammation. As discussed in this Review, much remains to be discovered about how this interesting family of proteins functions in a diverse set of processes in metazoans and the functional roles srGAPs play in human disease.

A current view on contactin-4, -5, and -6: Implications in neurodevelopmental disorders

Contactins (Cntns) are a six-member subgroup of the immunoglobulin cell adhesion molecule superfamily (IgCAMs) with pronounced brain expression and function. Recent genetic studies of neuropsychiatric disorders have pinpointed contactin-4 (CNTN4), contactin-5 (CNTN5) and contactin-6 (CNTN6) as candidate genes in neurodevelopmental disorders, particularly in autism spectrum disorders (ASDs), but also in intellectual disability, schizophrenia (SCZ), attention-deficit hyperactivity disorder (ADHD), bipolar disorder (BD), alcohol use disorder (AUD) and anorexia nervosa (AN). This suggests that they have important functions during neurodevelopment. This suggestion is supported by data showing that neurite outgrowth, cell survival and neural circuit formation can be affected by disruption of these genes. Here, we review the current genetic data about their involvement in neuropsychiatric disorders and explore studies on how null mutations affect mouse behavior. Finally, we highlight to role of protein-protein interactions in the potential mechanism of action of Cntn4, -5 and -6 and emphasize that complexes with other membrane proteins may play a role in neuronal developmental functions.

Association of Cell Adhesion Molecules Contactin-6 and Latrophilin-1 Regulates Neuronal Apoptosis

In view of important neurobiological functions of the cell adhesion molecule contactin-6 (Cntn6) that have emerged from studies on null-mutant mice and autism spectrum disorders patients, we set out to examine pathways underlying functions of Cntn6 using a proteomics approach. We identified the cell adhesion GPCR latrophilin-1 (Lphn1, a.k.a. CIRL1/CL, ADGRL1) as a binding partner for Cntn6 forming together a heteromeric cis-complex. Lphn1 expression in cultured neurons caused reduction in neurite outgrowth and increase in apoptosis, which was rescued by coexpression of Cntn6. In cultured neurons derived from Cntn6^-/- mice, Lphn1 knockdown reduced apoptosis, suggesting that the observed apoptosis was Lphn1-dependent. In line with these data, the number of apoptotic cells was increased in the cortex of Cntn6^-/- mice compared to wild-type littermate controls. These results show that Cntn6 can modulate the activity of Lphn1 by direct binding and suggests that Cntn6 may prevent apoptosis thereby impinging on neurodevelopment.

Urological Findings in Beckwith-Wiedemann Syndrome With Chromosomal Duplications of 11p15.5: Evaluation and Management

Beckwith-Wiedemann Syndrome (BWS) is an overgrowth disorder with various congenital anomalies. Although the most classic constellation includes macrosomia, macroglossia, and omphalocele, nephrourological findings are commonly associated with BWS. Clinical presentation is highly variable because of its complex molecular heterogeneity, which involves changes in DNA methylation and disruption of growth regulatory genes. We report 3 pediatric patients, ages 13 months to 3 years old, who presented with clinical features consistent with BWS. A variety of nephrourological abnormalities were also noted, including posterior urethral valves, hydroureteronephrosis, and undescended testes. Genetic testing for all 3 patients revealed duplication of the region chromosome 11p15.5.

Novel microduplication of CHL1 gene in a patient with autism spectrum disorder: a case report and a brief literature review

BACKGROUND

The cell adhesion molecule L1-like (CHL1 or CALL) gene is located on chromosome 3p26.3, and it is highly expressed in the central and peripheral nervous systems. The protein encoded by this gene is a member of the L1 family of neural cell adhesion molecules, and it plays a role in nervous system development and synaptic plasticity. Moreover, studies of mice have revealed that CHL1 is a prime candidate gene for a dosage-sensitive autosomal form of mental retardation. To date, four patients with a microdeletion and two with a microduplication of 3p26.3 encompassing only the CHL1 gene have been reported in literature.

CASE PRESENTATION

In the present study, we have described a 16-month-old boy with autism spectrum disorder (ASD), developmental delay and minor dysmorphic facial features. This is the first report of a duplication of 3p26.3 including only the CHL1 gene in an ASD patient, and this duplication is the smallest reported to date in this gene. We also reviewed CHL1 gene mutation cases and examined whether this gene has an important role in cognitive function.

CONCLUSIONS

We conclude that both CHL1 deletions and duplications are likely responsible for the patient's impaired cognitive function, and CHL1 may be an intriguing ASD candidate gene.

Morphological and behavioral characterization of adult mice deficient for SrGAP3

SrGAP3 belongs to the family of Rho GTPase proteins. These proteins are thought to play essential roles in development and in the plasticity of the nervous system. SrGAP3-deficient mice have recently been created and approximately 10 % of these mice developed a hydrocephalus and died shortly after birth. The others survived into adulthood, but displayed neuroanatomical alteration, including increased ventricular size. We now show that SrGAP3-deficient mice display increased brain weight together with increased hippocampal volume. This increase was accompanied by an increase of the thickness of the stratum oriens of area CA1 as well as of the thickness of the molecular layer of the dentate gyrus (DG). Concerning hippocampal adult neurogenesis, we observed no significant change in the number of proliferating cells. The density of doublecortin-positive cells also did not vary between SrGAP3-deficient mice and controls. By analyzing Golgi-impregnated material, we found that, in SrGAP3-deficient mice, the morphology and number of dendritic spines was not altered in the DG. Likewise, a Sholl-analysis revealed no significant changes concerning dendritic complexity as compared to controls. Despite the distinct morphological alterations in the hippocampus, SrGAP3-deficient mice were relatively inconspicuous in their behavior, not only in the open-field, nest building but also in the Morris water-maze. However, the SrGAP3-deficient mice showed little to no interest in burying marbles; a behavior that is seen in some animal models related to autism, supporting the view that SrGAP3 plays a role in neurodevelopmental disorders.

Chromosome r(3)(p25.3q29) in a Patient with Developmental Delay and Congenital Heart Defects: A Case Report and a Brief Literature Review

Ring chromosome 3, r(3), is an extremely rare cytogenetic abnormality with clinical heterogeneity and only 12 cases reported in the literature. Here, we report a 1-year-old girl presenting distinctive facial features, developmental delay, and congenital heart defects with r(3) and a ∼10-Mb deletion of chromosome 3pterp25.3 (61,891-9,979,408) involving 42 known genes which was detected using G-banding karyotyping and CytoScan 750K-Array. The breakpoints in r(3) were mapped at 3p25.3 and 3q29. We also analyzed the available information on the clinical features of the reported cases with r(3) and 3p deletion syndrome in order to provide more valuable information of genotype-phenotype correlations. To our knowledge, this is the largest detected fragment described in r(3) cases and the second r(3) study using whole-genome microarray.

A case of 3p deletion syndrome associated with cerebellar hemangioblastoma

We described clinical course of a 24-year-old woman with 3p deletion syndrome associated with cerebellar hemangioblastoma at the age of 16 years old. She presented dysmorphic facial features, growth retardation and severe psychomotor retardation associated with 3p deletion syndrome. We identified de novo 3p deletion encompassing p25 by using array-based comparative genomic hybridization, where causative gene of von Hippel-Lindau (VHL) disease located. Surgical therapy for cerebellar hemangioblastoma was performed, and histological examination was consistent in cerebellar hemangioblastoma. She showed no other tumors associated VHL disease till 24 years old. This is the first case report of a patient with 3p deletion syndrome whose cerebellar hemangioblastoma may be associated with VHL disease. Repeat imaging studies were recommended for the patients with 3p deletion syndrome.

SrGAP3 knockout mice display enlarged lateral ventricles and specific cilia disturbances of ependymal cells in the third ventricle

In several mouse models of mental retardation, ventricular enlargements have been observed. Mutation in the SrGAP3 gene residing on chromosome 3p25 has previously been associated with intellectual disability in humans. In addition, SrGAP3 is related to Rho-GAPs signaling pathways, which play essential roles in the development and plasticity of the nervous system. About 10 % of postnatal homozygous SrGAP3-deficient mice die due to hydrocephalus, whereas the remaining mice survive into adulthood but display enlarged ventricles. We analyze the ventricular enlargement of these mice by performing a post-mortem MRI approach. We found a more than 15-fold enlargement of the lateral ventricles of homozygous SrGAP3-deficient mice. Moreover, we demonstrate that this phenotype was not accompanied by a stenosis of the aqueduct. Instead, SrGAP3 knockout mice displayed reduced densities of cilia of ependymal cells in These third ventricle compared to age-matched controls. This results indicate that the ventricular enlargement may be due to ciliopathy.

F-BAR family proteins, emerging regulators for cell membrane dynamic changes-from structure to human diseases

Eukaryotic cell membrane dynamics change in curvature during physiological and pathological processes. In the past ten years, a novel protein family, Fes/CIP4 homology-Bin/Amphiphysin/Rvs (F-BAR) domain proteins, has been identified to be the most important coordinators in membrane curvature regulation. The F-BAR domain family is a member of the Bin/Amphiphysin/Rvs (BAR) domain superfamily that is associated with dynamic changes in cell membrane. However, the molecular basis in membrane structure regulation and the biological functions of F-BAR protein are unclear. The pathophysiological role of F-BAR protein is unknown. This review summarizes the current understanding of structure and function in the BAR domain superfamily, classifies F-BAR family proteins into nine subfamilies based on domain structure, and characterizes F-BAR protein structure, domain interaction, and functional relevance. In general, F-BAR protein binds to cell membrane via F-BAR domain association with membrane phospholipids and initiates membrane curvature and scission via Src homology-3 (SH3) domain interaction with its partner proteins. This process causes membrane dynamic changes and leads to seven important cellular biological functions, which include endocytosis, phagocytosis, filopodium, lamellipodium, cytokinesis, adhesion, and podosome formation, via distinct signaling pathways determined by specific domain-binding partners. These cellular functions play important roles in many physiological and pathophysiological processes. We further summarize F-BAR protein expression and mutation changes observed in various diseases and developmental disorders. Considering the structure feature and functional implication of F-BAR proteins, we anticipate that F-BAR proteins modulate physiological and pathophysiological processes via transferring extracellular materials, regulating cell trafficking and mobility, presenting antigens, mediating extracellular matrix degradation, and transmitting signaling for cell proliferation.

Trisomy 1q41-qter and monosomy 3p26.3-pter in a family with a translocation (1;3): further delineation of the syndromes

Background

Trisomy 1q and monosomy 3p deriving from a t(1;3) is an infrequent event. The clinical characteristics of trisomy 1q41-qter have been described but there is not a delineation of the syndrome. The 3p25.3-pter monosomy syndrome (MIM 613792) characteristics include low birth weight, microcephaly, psychomotor and growth retardation and abnormal facies.

Case presentation

A 2 years 8 months Mexican mestizo male patient was evaluated due to a trisomy 1q and monosomy 3p derived from a familial t(1;3)(q41;q26.3). Four female carriers of the balanced translocation and one relative that may have been similarly affected as the proband were identified. The implicated chromosomal regions were defined by microarray analysis, the patient had a trisomy 1q41-qter of 30.3 Mb in extension comprising about 240 protein coding genes and a monosomy 3p26.3-pter of 1.7 Mb including only the genes CNTN6 (MIM 607220) and CHL1 (MIM 607416), which have been implicated in dendrite development. Their contribution to the phenotype, regarding the definition of trisomy 1q41-qter and monosomy 3p26.3-pter syndromes are discussed.

Conclusion

We propose that a trisomy 1q41-qter syndrome should be considered in particular when the following characteristics are present: postnatal growth delay, macrocephaly, wide fontanelle, triangular facies, frontal bossing, thick eye brows, down slanting palpebral fissures, hypertelorism, flat nasal bridge, hypoplasic nostrils, long filtrum, high palate, microretrognathia, ear abnormalities, neural abnormalities (in particular ventricular dilatation), psychomotor developmental delay and mental retardation. Our patient showed most of these clinical characteristics with exception of macrocephaly, possibly due to a compensatory effect by haploinsufficiency of the two genes lost from 3p. The identification of carriers has important implications for genetic counseling as the risk of a new born with either a der(3) or der(1) resulting from an adjacent-1 segregation is of 25% for each of them, as the products of adjacent-2 or 3:1 segregations are not expected to be viable.

Loss-of-function variants of SETD5 cause intellectual disability and the core phenotype of microdeletion 3p25.3 syndrome

Intellectual disability (ID) has an estimated prevalence of 2-3%. Due to its extreme heterogeneity, the genetic basis of ID remains elusive in many cases. Recently, whole exome sequencing (WES) studies revealed that a large proportion of sporadic cases are caused by de novo gene variants. To identify further genes involved in ID, we performed WES in 250 patients with unexplained ID and their unaffected parents and included exomes of 51 previously sequenced child-parents trios in the analysis. Exome analysis revealed de novo intragenic variants in SET domain-containing 5 (SETD5) in two patients. One patient carried a nonsense variant, and the other an 81 bp deletion located across a splice-donor site. Chromosomal microarray diagnostics further identified four de novo non-recurrent microdeletions encompassing SETD5. CRISPR/Cas9 mutation modelling of the two intragenic variants demonstrated nonsense-mediated decay of the resulting transcripts, pointing to a loss-of-function (LoF) and haploinsufficiency as the common disease-causing mechanism of intragenic SETD5 sequence variants and SETD5-containing microdeletions. In silico domain prediction of SETD5, a predicted SET domain-containing histone methyltransferase (HMT), substantiated the presence of a SET domain and identified a novel putative PHD domain, strengthening a functional link to well-known histone-modifying ID genes. All six patients presented with ID and certain facial dysmorphisms, suggesting that SETD5 sequence variants contribute substantially to the microdeletion 3p25.3 phenotype. The present report of two SETD5 LoF variants in 301 patients demonstrates a prevalence of 0.7% and thus SETD5 variants as a relatively frequent cause of ID.

A terminal 3p26.3 deletion is not associated with dysmorphic features and intellectual disability in a four-generation family

Terminal deletions of the distal part of the short arm of chromosome 3 cause a wide range of phenotypes from normal to dysmorphic including microcephaly, developmental delay and intellectual disability. We studied the clinical consequences of a terminal deletion of the short arm of chromosome 3 in four generations of a family. The index patient is a14-month-old boy with microcephaly, corpus callosum dysgenesis, and minor dysmorphic features. Single Nucleotide Polymorphism (SNP) array analysis detected a duplication on the long arm of chromosome 6. His apparently healthy mother carries the same 6q duplication, but as an unexpected finding a terminal deletion of 2.9 Mb of the short arm of chromosome 3 was observed. Further co-segregation analysis in the family for the chromosome 3 deletion showed that with the exception of the sister of the index who has autism, speech delay, and learning problems, family members in four generations of this family are carrier of this 3p deletion and apparently healthy. To our knowledge, this is the first report of a study of this terminal 3p deletion in four generations. In this report, we review the literature on terminal 3p deletions and discuss the importance of molecular testing and reporting of copy number variants to achieve accurate genetic counseling in prenatal and postnatal screening.

Aberrant Rho GTPases signaling and cognitive dysfunction: in vivo evidence for a compelling molecular relationship

Rho GTPases are key intracellular signaling molecules that coordinate dynamic changes in the actin cytoskeleton, thereby stimulating a variety of processes, including morphogenesis, migration, neuronal development, cell division and adhesion. Deviations from normal Rho GTPases activation state have been proposed to disrupt cognition and synaptic plasticity. This review focuses on the functional consequences of genetic ablation of upstream and downstream Rho GTPases molecules on cognitive function and neuronal morphology and connectivity. Available information on this issue is described and compared to that gained from mice carrying mutations in the most studied Rho GTPases and from pharmacological in vivo studies in which brain Rho GTPases signaling was modulated. Results from reviewed literature provide definitive evidence of a compelling link between Rho GTPases signaling and cognitive function, thus supporting the notion that Rho GTPases and their downstream effectors may represent important therapeutic targets for disorders associated with cognitive dysfunction.

Genetic basis of congenital cardiovascular malformations

Cardiovascular malformations are a singularly important class of birth defects and due to dramatic improvements in medical and surgical care, there are now large numbers of adult survivors. The etiologies are complex, but there is strong evidence that genetic factors play a crucial role. Over the last 15 years there has been enormous progress in the discovery of causative genes for syndromic heart malformations and in rare families with Mendelian forms. The rapid characterization of genomic disorders as major contributors to congenital heart defects is also notable. The genes identified encode many transcription factors, chromatin regulators, growth factors and signal transduction proteins- all unified by their required roles in normal cardiac development. Genome-wide sequencing of the coding regions promises to elucidate genetic causation in several disorders affecting cardiac development. Such comprehensive studies evaluating both common and rare variants would be essential in characterizing gene-gene interactions, as well as in understanding the gene-environment interactions that increase susceptibility to congenital heart defects.

De novo loss-of-function mutations in SETD5, encoding a methyltransferase in a 3p25 microdeletion syndrome critical region, cause intellectual disability

To identify further Mendelian causes of intellectual disability (ID), we screened a cohort of 996 individuals with ID for variants in 565 known or candidate genes by using a targeted next-generation sequencing approach. Seven loss-of-function (LoF) mutations-four nonsense (c.1195A>T [p.Lys399(∗)], c.1333C>T [p.Arg445(∗)], c.1866C>G [p.Tyr622(∗)], and c.3001C>T [p.Arg1001(∗)]) and three frameshift (c.2177_2178del [p.Thr726Asnfs(∗)39], c.3771dup [p.Ser1258Glufs(∗)65], and c.3856del [p.Ser1286Leufs(∗)84])-were identified in SETD5, a gene predicted to encode a methyltransferase. All mutations were compatible with de novo dominant inheritance. The affected individuals had moderate to severe ID with additional variable features of brachycephaly; a prominent high forehead with synophrys or striking full and broad eyebrows; a long, thin, and tubular nose; long, narrow upslanting palpebral fissures; and large, fleshy low-set ears. Skeletal anomalies, including significant leg-length discrepancy, were a frequent finding in two individuals. Congenital heart defects, inguinal hernia, or hypospadias were also reported. Behavioral problems, including obsessive-compulsive disorder, hand flapping with ritualized behavior, and autism, were prominent features. SETD5 lies within the critical interval for 3p25 microdeletion syndrome. The individuals with SETD5 mutations showed phenotypic similarity to those previously reported with a deletion in 3p25, and thus loss of SETD5 might be sufficient to account for many of the clinical features observed in this condition. Our findings add to the growing evidence that mutations in genes encoding methyltransferases regulating histone modification are important causes of ID. This analysis provides sufficient evidence that rare de novo LoF mutations in SETD5 are a relatively frequent (0.7%) cause of ID.

Prenatal diagnosis of a distal 3p deletion associated with fetoplacental chromosomal discrepancy and confined placental mosaicism detected by array comparative genomic hybridization

OBJECTIVE

This study is aimed at prenatal diagnosis of a distal 3p deletion associated with fetoplacental chromosomal discrepancy and confined placental mosaicism, and providing evidence for the limitation of array comparative genomic hybridization (aCGH) on placental tissues for molecular cytogenetic characterization of prenatally detected aneuploidy.

CASE REPORT

A 30-year-old woman underwent amniocentesis at 18 weeks of gestation because of maternal anxiety. Results of amniocentesis revealed a distal deletion of chromosome 3p. A malformed female fetus was delivered at 20 weeks of gestation with brachycephaly and facial dysmorphisms, and a cytogenetic analysis of the cord blood revealed a karyotype of 46,XX,del(3)(p26.1),inv(9)(p12q13). A whole-genome aCGH on uncultured cord blood and placental tissue was performed. The aCGH on cord blood revealed a 7.4-Mb deletion at 3p26.3-p26.1. However, the aCGH on placental tissue revealed a 32.42-Mb gene dosage increase at 3p26.1-p22.1 and a 26.28-Mb gene dosage increase at 1p36.33-p36.11 in addition to a 7.4-Mb deletion at 3p26.3-p26.1, indicating confined placental mosaicism for partial trisomy 3p (3p26.1→p22.1) and mosaicism for partial trisomy 1p (1p36.33→p36.11). The 7.4-Mb deleted region of 3p26.3-p26.1 contained the following genes: CHL1, CNTN4, CRBN, LRRN1, and ITPR1.

CONCLUSION

Fetal tissue and amniocytes offer more reliable resources for aCGH characterization of prenatally detected aneuploidy compared with placental tissues. A molecular cytogenetic evaluation of prenatally detected aneuploidy using placental tissue should raise concerns of confined placental mosaicism and fetoplacental chromosomal discrepancy.

Deletion of 3p25.3 in a patient with intellectual disability and dysmorphic features with further definition of a critical region

Several recent reports of interstitial deletions at the terminal end of the short arm of chromosome 3 have helped to define the critical region whose deletion causes 3p deletion syndrome. We report on an 11-year-old girl with intellectual disability, obsessive-compulsive tendencies, hypotonia, and dysmorphic facial features in whom a 684 kb interstitial 3p25.3 deletion was characterized using array-CGH. This deletion overlaps with interstitial 3p25 deletions reported in three recent case reports. These deletions share a 124 kb overlap region including only three RefSeq annotated genes, THUMPD3, SETD5, and LOC440944. The current patient had phenotypic similarities, including intellectual disability, hypotonia, depressed nasal bridge, and long philtrum, with previously reported patients, while she did not have the cardiac defects, seizures ormicrocephaly reported in patients with larger deletions. Therefore, this patient furthers our knowledge of the consequences of 3p deletions, while suggesting genotype-phenotype correlations.

Pure partial monosomy 3p (3p25.3 → pter): prenatal diagnosis and array comparative genomic hybridization characterization

OBJECTIVE

The purpose of this case report is to present prenatal diagnosis and molecular cytogenetic characterization of pure partial monosomy 3p (3p25.3 → pter) by array comparative genomic hybridization (aCGH) and quantitative fluorescent polymerase chain reaction (QF-PCR) on uncultured amniocytes.

CASE REPORT

A 35-year-old, gravida 2, para 0, woman underwent amniocentesis at 19 weeks of gestation because of advanced maternal age. Her husband was 37 years of age. She had experienced one intrauterine fetal death. Amniocentesis during this pregnancy revealed a distal deletion of chromosome 3p. The parental karyotypes were normal. Prenatal ultrasonography findings were unremarkable. At 22 weeks of gestation, she underwent repeated amniocentesis, and aCGH investigation using CytoChip Oligo Array on uncultured amniocytes revealed a 9.29-Mb deletion of 3p26.3p25.3 [arr 3p26.3p25.3 (64,096-9,357,258 bp) ×1] encompassing the genes of CHL1, CNTN4, CRBN, LRRN1, ITPR1, and SRGAP3, but not involving the markers D3S1263 and D3S3594. Polymorphic DNA marker analysis on uncultured amniocytes showed a paternal origin of the deletion. Cytogenetic analysis of cultured amniocytes revealed a karyotype of 46,XX,del(3)(p25.3). At 24 weeks of gestation, prenatal ultrasonography findings of the brain, heart, and other internal organs were unremarkable. The pregnancy was subsequently terminated, and an 886-g female fetus was delivered with brachycephaly, hypertelorism, a short and thick nose, micrognathia and low-set ears.

CONCLUSION

In this case, aCGH has characterized a 3p deleted region with haploinsufficiency of the neurodevelopmental genes associated with cognitive deficit and mental retardation but without involvement of the congenital heart disease susceptibility locus, and QF-PCR has determined a paternal origin of the deletion. aCGH and QF-PCR help to delineate the genomic imbalance in prenatally detected de novo chromosome aberration, and the information acquired is useful for genetic counseling.

The cellular function of srGAP3 and its role in neuronal morphogenesis

The Slit-Robo GTPase activating protein 3 (srGAP3) dynamically regulates cytoskeletal reorganisation through inhibition of the Rho GTPase Rac1 and interaction with actin remodelling proteins. SrGAP3-mediated reorganisation of the actin cytoskeleton is crucial for the normal development of dendritic spines and loss of srGAP3 leads to abnormal synaptic activity and impaired cognitive behaviours in mice, which is reminiscent of an association between disrupted srGAP3 and intellectual disability in humans. Additionally, srGAP3 has been implicated to act downstream of Slit-Robo signalling in commissural axons of the spinal cord. Thus, srGAP3-mediated cytoskeletal reorganisation has an important influence on a variety of neurodevelopmental processes, which may be required for normal cognitive function.

A tumor suppressor role for srGAP3 in mammary epithelial cells

srGAP3, a member of the Slit-Robo sub-family of Rho GTPase-activating proteins (Rho GAPs), controls actin and microtubule dynamics through negative regulation of Rac. Here, we describe a potential role for srGAP3 as a tumor suppressor in mammary epithelial cells. We show that RNAi-mediated depletion of srGAP3 promotes Rac dependent, anchorage-independent growth of partially transformed human mammary epithelial cells (HMECs). Furthermore, srGAP3 expression is absent, or significantly reduced in 7/10 breast cancer cell lines compared with normal HMECs. Re-expression of srGAP3 in a subset of these cell lines inhibits both anchorage-independent growth and cell invasion in a GAP-dependent manner, and this is accompanied by an increase in phosphorylation of the ezrin/radixin/moesin (ERM) family proteins and myosin light chain 2 (MLC2). Inhibition of the Rho regulated kinase, ROCK, reduces ERM and MLC2 phosphorylation and restores invasion. We conclude that srGAP3 has tumor suppressor-like activity in HMECs, likely through its activity as a negative regulator of Rac1.

A rare chromosome 3 imbalance and its clinical implications

The duplication of chromosome 3q is a rare disorder with varying chromosomal breakpoints and consequently symptoms. Even rarer is the unbalanced outcome from a parental inv(3) resulting in duplicated 3q and a deletion of 3p. Molecular karyotyping should aid in precisely determining the length and breakpoints of the 3q+/3p− so as to better understand a child's future development and needs. We report a case of an infant male with a 57.5 Mb duplication from 3q23-qter. This patient also has an accompanying 1.7 Mb deletion of 3p26.3. The duplicated segment in this patient encompasses the known critical region of 3q26.3-q27, which is implicated in the previously reported 3q dup syndrome; however, the accompanying 3p26.3 deletion is smaller than the previously reported cases. The clinical phenotype of this patient relates to previously reported cases of 3q+ that may suggest that the accompanying 1.7 Mb heterozygous deletion is not clinically relevant. Taken together, our data has refined the location and extent of the chromosome 3 imbalance, which will aid in better understanding the molecular underpinning of the 3q syndrome.

Partial monosomy 21 (q11.2→q21.3) combined with 3p25.3→pter monosomy due to an unbalanced translocation in a patient presenting dysmorphic features and developmental delay

We describe a female patient of 1 year and 5 months-old, referred for genetic evaluation due to neuropsychomotor delay, hearing impairment and dysmorphic features. The patient presents a partial chromosome 21 monosomy (q11.2→q21.3) in combination with a chromosome 3p terminal monosomy (p25.3→pter) due to an unbalanced de novo translocation. The translocation was confirmed by fluorescence in situ hybridization (FISH) and the breakpoints were mapped with high resolution array. After the combined analyses with these techniques the final karyotype was defined as 45,XX,der(3)t(3;21)(p25.3;q21.3)dn,-21.ish der(3)t(3;21)(RP11-329A2-,RP11-439F4-,RP11-95E11-,CTB-63H24+).arr 3p26.3p25.3(35,333-10,888,738))×1,21q11.2q21.3(13,354,643-27,357,765)×1. Analysis of microsatellite DNA markers pointed to a paternal origin for the chromosome rearrangement. This is the first case described with a partial proximal monosomy 21 combined with a 3p terminal monosomy due to a de novo unbalanced translocation.

Interstitial 3p25.3-p26.1 deletion in a patient with intellectual disability

Interstitial deletions of the short arm of chromosome 3 are rare. We report on a 3-year-old girl with intellectual disability, muscular hypotonia, strabismus, and facial anomalies in whom an interstitial 1.24 Mb deletion in 3p25.3-p26.1 was detected by SNP array analysis. The deleted region harbors 11 RefSeq genes including CAV3 and SRGAP3/MEGAP, which had been associated with muscle disorders and intellectual disability, respectively. The deletion overlaps with a slightly larger deletion in a girl with a more complex phenotype including congenital heart defect and epilepsy, which indicates that haploinsufficiency of one or several of the genes in the deleted interval causes intellectual deficits, but not heart defects or epilepsy. Thus, the patient broadens our knowledge of the phenotypic consequences of deletions in 3p25.3-p26.1 and facilitates genotype-phenotype correlations for chromosome aberrations of this region.

A novel contiguous gene deletion of AVPR2 and ARHGAP4 genes in male dizygotic twins with nephrogenic diabetes insipidus and intellectual disability

The clinical features of loss of ARHGAP4 function remain unclear despite several reports of different patterns of deletions inactivating different functional regions of the protein. The protein encoded by ARHGAP4 is thought to function as a Rho GTPase activating protein. Characterization of the genetic defect causing X-linked nephrogenic diabetes insipidus (NDI) and intellectual disability in two dizygotic twin brothers revealed a novel contiguous deletion of 17,905 bp encompassing the entire AVPR2 gene and extending into intron 7 of the ARHGAP4 gene. Examination of their mother showed that she was a carrier of this deletion. An attempt was made to distinguish the putative clinical signs of an ARHGAP4 deletion from the well-defined phenotype of X-linked NDI caused by an AVPR2 gene deletion. By reviewing all characterized deletions encompassing ARHGAP4, we reconsider the potential role of ARHGAP4 in cognition.

Microdeletion on 3p25 in a patient with features of 3p deletion syndrome

The rare 3p deletion syndrome presents with a spectrum of anomalies caused by deletions of variable lengths within the short arm of chromosome 3. While most of these deletions involve the 3p terminus, interstitial deletions may also give rise to features of the syndrome. We have detected an interstitial deletion of 643 kb in a patient who displayed many of the typical 3p deletion features. This patient had a number of findings in common with a previously reported patient, who had a 1.6 Mb interstitial deletion, including cognitive handicap, seizures, and congenital heart defects. A 518 kb region of overlap containing 12 genes may prove to be a critical region for some of these features. The putative functions of several genes, such as CRELD1, SRGAP3, CAMK1, TADA3, and MTMR14 are discussed with respect to their potential involvement in the 3p deletion syndrome phenotype. We suggest that this 518 kb area of overlap may define a critical region, which when deleted, can give rise to the 3p deletion syndrome phenotype.

Unintended diagnosis of Von Hippel Lindau syndrome using Array Comparative Genomic Hybridization (CGH): counseling challenges arising from unexpected information

Array Comparative Genomic Hybridization (array CGH) is a powerful tool for identifying genomic imbalances and providing a diagnosis in individuals with a normal karyotype. It has been particularly useful in the investigation of individuals with developmental delay +/-, dysmorphic features and/or multiple congenital abnormalities. However, this non-targeted method of scanning the whole genome can reveal unexpected information. We present a case where array CGH identified the cause of a proband's moderate mental retardation by discovery of a de novo deletion of chromosome 3p25.3. This deletion was shown to contain at least 25 genes including the VHL gene, the deletion or mutation of which leads to Von Hippel Lindau (VHL) syndrome. Presymptomatic testing for VHL is usually offered after appropriate genetic counseling about the implications of this condition. Therefore, scanning the genome by array CGH presents a number of challenges for the genetic counselor. We suggest that further understanding of the psychosocial effects of array CGH is needed in order for appropriate pre- and post-test counseling to be provided.

A miRNA signature in leukocytes from sporadic amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive and seriously disabling adult-onset neurological disease. Accumulating evidence indicates that various miRNAs, expressed in a spatially and temporally controlled manner in the brain, play a key role in neuronal development. In addition, misregulation of microRNAs contributes to some mental disorders and neurodegeneration diseases. Here, we analyzed the expression profiles of 911 human miRNAs using microarray technology in leukocytes, the most readily available human tissue cells, obtained from 8 patients affected by sporadic amyotrophic lateral sclerosis (sALS) and 12 healthy controls. An independent group of 14 sALS patients and 14 controls was used for validation by TaqMan real-time polymerase chain reaction assay. We identified 8 miRNAs that were significantly up- or downregulated in sALS patients as compared to healthy controls. The significant variations in miRNAs profiles detected in leukocytes have been related to miRNAs predominantly expressed in the nervous system. One of these miRNAs, miR-338-3p, has previously been shown to be de-regulated in ALS brains. This study, for the first time, detected specific microRNAs disease-related changes at an earlier stage of sALS. We suggest that miRNAs profiles found in the peripheral blood leukocytes from sALS patients can be relevant to understand the pathogenesis of sALS and/or used as biomarkers of the disease.

Srgap3⁻/⁻ mice present a neurodevelopmental disorder with schizophrenia-related intermediate phenotypes

Mutations in the SRGAP3 gene residing on chromosome 3p25 have previously been associated with intellectual disability. Genome-wide association studies have also revealed SRGAP3, together with genes from the same cellular network, as risk genes for schizophrenia. SRGAP3 regulates cytoskeletal dynamics through the RHO protein RAC1. RHO proteins are known to be involved in cytoskeletal reorganization during brain development to control processes such as synaptic plasticity. To elucidate the importance of SRGAP3 in brain development, we generated Srgap3-knockout mice. Ten percent of these mice developed a hydrocephalus and died before adulthood. Surviving mice showed various neuroanatomical changes, including enlarged lateral ventricles, white matter tracts, and dendritic spines together with molecular changes, including an increased basal activity of RAC1. Srgap3(-/-) mice additionally exhibited a complex behavioral phenotype. Behavioral studies revealed an impaired spontaneous alternation and social behavior, while long-term memory was unchanged. The animals also had tics. Lower locomotor activity was observed in male Srgap3(-/-) only. Srgap3(-/-) mice showed increased methylphenidate stimulation in males and an impaired prepulse inhibition in females. Together, the results show neurodevelopmental aberration in Srgap3(-/-) mice, with many of the observed phenotypes matching several schizophrenia-related intermediate phenotypes. Mutations of SRGAP3 may thus contribute to various neurodevelopmental disorders.