Papers by Laurence Colleaux
European Journal of Human Genetics, Mar 29, 2006
In the course of a systematic whole genome screening of patients with unexplained overgrowth synd... more In the course of a systematic whole genome screening of patients with unexplained overgrowth syndrome by microarray-based comparative genomic hybridisation (array-CGH), we have identified two children with nearly identical 6.5 Mb-long de novo interstitial deletions at 9q22.32 -q22.33. The clinical phenotype includes macrocephaly, overgrowth and trigonocephaly. In addition, both children present with psychomotor delay, hyperactivity and distinctive facial features. Further analysis with a high-resolution custom microarray covering the whole breakpoint intervals with fosmids mapped the deletion breakpoints within 100-kb intervals: although the deletion boundaries are different for the two patients, nearly the same genes are deleted in both cases. We suggest therefore that microdeletion of 9q22.32-q22.33 is a novel cause of overgrowth and mental retardation. Its association with distinctive facial features should help in recognising this novel phenotype.
European Journal of Human Genetics, Oct 21, 2009
Overgrowth syndromes are a heterogeneous group of conditions including endocrine hormone disorder... more Overgrowth syndromes are a heterogeneous group of conditions including endocrine hormone disorders, several genetic syndromes and other disorders with unknown etiopathogenesis. Among genetic causes, chromosomal deletions and duplications such as dup(4)(p16.3), dup(15)(q26qter), del(9)(q22.32q22.33), del(22)(q13) and del(5)(q35) have been identified in patients with overgrowth. Most of them, however, remain undetectable using banding karyotype analysis. In this study, we report on the analysis using a 1-Mb resolution array-based comparative genomic hybridization (CGH) of 93 patients with either a recognizable overgrowth condition (ie, Sotos syndrome or Weaver syndrome) or an unclassified overgrowth syndrome. Five clinically relevant imbalances (three duplications and two deletions) were identified and the pathogenicity of two additional anomalies (one duplication and one deletion) is discussed. Altered segments ranged in size from 0.32 to 18.2 Mb, and no recurrent abnormality was identified. These results show that array-CGH provides a high diagnostic yield in patients with overgrowth syndromes and point to novel chromosomal regions associated with these conditions. Although chromosomal deletions are usually associated with growth retardation, we found that the majority of the imbalances detected in our patients are duplications. Besides their importance for diagnosis and genetic counseling, our results may allow to delineate new contiguous gene syndromes associated with overgrowth, pointing to new genes, the deregulation of which may be responsible for growth defect.
Nature Communications
Oral-facial-digital (OFD) syndromes are a heterogeneous group of congenital disorders characteriz... more Oral-facial-digital (OFD) syndromes are a heterogeneous group of congenital disorders characterized by malformations of the face and oral cavity, and digit anomalies. Mutations within 12 cilia-related genes have been identified that cause several types of OFD, suggesting that OFDs constitute a subgroup of developmental ciliopathies. Through homozygosity mapping and exome sequencing of two families with variable OFD type 2, we identified distinct germline variants in INTS13, a subunit of the Integrator complex. This multiprotein complex associates with RNA Polymerase II and cleaves nascent RNA to modulate gene expression. We determined that INTS13 utilizes its C-terminus to bind the Integrator cleavage module, which is disrupted by the identified germline variants p.S652L and p.K668Nfs*9. Depletion of INTS13 disrupts ciliogenesis in human cultured cells and causes dysregulation of a broad collection of ciliary genes. Accordingly, its knockdown in Xenopus embryos leads to motile cilia...
Mutations in the XNP/ATR-X gene, located in Xq13.3, are associated with several X linked mental r... more Mutations in the XNP/ATR-X gene, located in Xq13.3, are associated with several X linked mental retardation syndromes, the best known being thalassaemia with mental retardation (ATR-X). The XNP/ATR-X protein belongs to the family of SWI/SNF DNA helicases and contains three C2-C2 type zinc fingers of unknown function. Previous studies have shown that 65% of mutations of XNP have been found within the zinc finger domain (encoded by exons 7, 8, and the beginning of exon 9) while 35% of the mutations have been found in the helicase domain extending over 3 kb at the C-terminus of the protein. Although diVerent types of mutations have been identified, no specific genotypephenotype correlation has been found, suggesting that gene alteration leads to a loss of function irrespective of mutation type. Our aims were to understand the function of the XNP/ATR-X protein better, with specific attention to the functional consequences of mutations to the zinc finger domain. We used monoclonal antibodies directed against the XNP/ ATR-X protein and performed immunocytochemical and western blot analyses, which showed altered or absent XNP/ ATR-X expression in cells of aVected patients. In addition, we used in vitro experiments to show that the zinc finger domain can mediate double stranded DNA binding and found that the DNA binding capacity of mutant forms in ATR-X patients is severely reduced. These data provide insights into the understanding of the functional significance of XNP/ ATR-X mutations.
ABSTRACTOral-facial-digital syndromes (OFD) are a heterogeneous group of congenital disorders cha... more ABSTRACTOral-facial-digital syndromes (OFD) are a heterogeneous group of congenital disorders characterized by malformations of the face and oral cavity, and digit anomalies. To date, mutations in 12 ciliary-related genes have been identified that cause several types of OFD, suggesting that OFDs constitute a subgroup of developmental ciliopathies. Through homozygosity mapping and exome sequencing of two families with variable OFD type 2, we identified distinct germline mutations inINTS13, a subunit of the Integrator complex. This 14-component complex associates with RNAPII and can cleave nascent RNA to modulate gene expression. We determined that INTS13 utilizes a discrete domain within its C-terminus to bind the Integrator cleavage module, which is disrupted by the identified germlineINTS13mutations. Depletion ofINTS13disrupts ciliogenesis in human cultured cells and causes dysregulation of a broad collection of ciliary genes. Accordingly, its knockdown inXenopusembryos lead to mot...
Psychiatric Genetics, 2008
Objectives Autism (MIM#209850) and schizophrenia (MIM#181500) are both neurodevelopmental psychia... more Objectives Autism (MIM#209850) and schizophrenia (MIM#181500) are both neurodevelopmental psychiatric disorders characterized by a highly genetic component. Homeogenes and forkhead genes encode transcription factors, which have been involved in brain development and cell differentiation. Thus, they are relevant candidate genes for psychiatric disorders. Genetic studies have reported an association between autism and DLX2, HOXA1, EN2, ARX, and FOXP2 genes whereas only three studies of EN2, OTX2, and FOXP2 were performed on schizophrenia. Interestingly, most of these candidate genes contain trinucleotide repeats coding for polyamino acid stretch in which instability can be the cause of neurodevelopmental disorders. Our goal was to identify variations of coding trinucleotide repeats in schizophrenia, autism, and idiopathic mental retardation. Methods We screened the coding trinucleotide repeats of OTX1, EN1, DLX2, HOXA1, and FOXP2 genes in populations suffering from schizophrenia (247 patients), autism (98 patients), and idiopathic mental retardation (56 patients), and compared them with control populations (112 super controls and 202 healthy controls). Results Novel deletions and insertions of coding trinucleotide repeats were found in the DLX2, HOXA1, and FOXP2 genes. Most of these variations were detected in controls and no difference in their distribution was observed between patient and control groups. Two different polymorphisms in FOXP2 were, however, found only in autistic patients and the functional consequences of these variations of repeats have to be characterized and correlated to particular clinical features. This study did not identify specific disease risk variants of trinucleotide repeats in OTX1, EN1, DLX2, HOXA1, and FOXP2 candidate genes in neurodevelopmental psychiatric disorders. Psychiatr
Journal of Medical Genetics, 2005
Journal of Medical Genetics, 2004
Journal of Medical Genetics, 2000
Mutations in the XNP/ATR-X gene, located in Xq13.3, are associated with several X linked mental r... more Mutations in the XNP/ATR-X gene, located in Xq13.3, are associated with several X linked mental retardation syndromes, the best known being thalassaemia with mental retardation (ATR-X). The XNP/ATR-X protein belongs to the family of SWI/SNF DNA helicases and contains three C2-C2 type zinc fingers of unknown function. Previous studies have shown that 65% of mutations of XNP have been found within the zinc finger domain (encoded by exons 7, 8, and the beginning of exon 9) while 35% of the mutations have been found in the helicase domain extending over 3 kb at the C-terminus of the protein. Although diVerent types of mutations have been identified, no specific genotypephenotype correlation has been found, suggesting that gene alteration leads to a loss of function irrespective of mutation type. Our aims were to understand the function of the XNP/ATR-X protein better, with specific attention to the functional consequences of mutations to the zinc finger domain. We used monoclonal antibodies directed against the XNP/ ATR-X protein and performed immunocytochemical and western blot analyses, which showed altered or absent XNP/ ATR-X expression in cells of aVected patients. In addition, we used in vitro experiments to show that the zinc finger domain can mediate double stranded DNA binding and found that the DNA binding capacity of mutant forms in ATR-X patients is severely reduced. These data provide insights into the understanding of the functional significance of XNP/ ATR-X mutations.
Journal of Medical Genetics, 2003
Journal of Medical Genetics, 2003
besity is a symptom of diagnostic value in multiple congenital anomaly-mental retardation syndrom... more besity is a symptom of diagnostic value in multiple congenital anomaly-mental retardation syndromes. While acquired non-specific weight gain related to drug intake or associated behavioural disorders occasionally occurs in the course of mental retardation, obesity is known to be a specific feature of several well defined conditions, including Bardet-Biedl syndrome, Prader-Willi syndrome, Cohen syndrome, fragile X syndrome, and several chromosomal anomalies. Yet a number of mentally retarded children with apparently early onset weight gain remain undiagnosed. Here, we report on a de novo deletion of chromosome 9q34 in two unrelated mentally retarded children with early onset obesity, distinctive facial features (brachycephaly, synophrys, anteverted nostrils, prognathism), sleep disturbances, and behavioural problems. FISH and microsatellite DNA analyses showed that the two children carried a similar small deletion (3 Mb) of the terminal long arm of chromosome 9 (del 9q34). We suggest therefore that the del 9q34 is a novel cause of syndromic obesity and mental retardation. Its association with distinctive facial features and behavioural problems should help in recognising this novel phenotype. Based on this observation, we suggest giving consideration to cryptic deletions of chromosome 9q34 in the diagnosis of unexplained obesity/ mental retardation syndromes Case 1 A boy was born to unrelated, healthy parents after a term pregnancy and normal delivery (birth weight 3200 g, length 50 cm, OFC 34.5 cm). He was hypotonic in the first months of life but no feeding difficulties were originally noted. Excessive weight gain with increased appetite and food seeking behaviour were noted at 30 months of age. At 5 years, his weight was 26 kg (>+3 SD), length 112 cm (+1 SD), and OFC 48 cm (-2 SD) and at 9 years his weight was 72 kg (>+ 6 SD), length 144 cm (+2 SD), and OFC 52.5 cm (-0.5 SD) (figs 1A-C and 2A). Distinctive facial features included brachycephaly, flat face, high forehead, synophrys, hypertelorism, anteverted nostrils, thin upper lip, prognathism, short hands, syndactyly of toes 2-3, (fig 1A ), and abnormal genitalia (cryptorchidism and hypospadias). He had major developmental delay (head control at 11 months, walked unaided at 23 months, no speech at 9 years). Cerebral MRI showed partial frontal atrophy. Psychometric evaluation at 9 years showed performance at a 2 year old level (DQ=50). He was hyperactive, with a short attention span, intolerance to frustration, and sleep disturbances with repeated night awakenings.
Journal of Medical Genetics, 1996
Genetic studies in families with X linked mental retardation have suggested the location ofsevera... more Genetic studies in families with X linked mental retardation have suggested the location ofseveral MR genes in the human q2 1 region. Since the establishment of cloned resources is an essential step towards the cloning of genes involved in inherited dis- eases, we built a yeast artificial chro- mosome (YAC) contig and an STS map of this part ofthe X chromosome. The contig, which extends from PGK1 in Xql3.3 to DXS1002 in Xq21.2, consists of 30 YACs mapped with 21 markers and spans about 6 Mb. The YAC contig was used as a frame- work to localise several previously known genes and CEPH/Genethon polymorphic markers, as well as to construct a physical map ofthe region surrounding one ofthese genes. We recently localised a presumed MR locus to the region flanked by DXS233 (proximal) and CHM (distal). In the pres- ent work, the zinc finger gene, ZNF6, has been shown to lie within this region and to be highly expressed in brain, making it a good candidate MR gene. Similarly the VDAC1 gene has been mapped between DXS986 and DXS72 and its candidate gene status for the Allan-Herndon-Dudley syn- drome is discussed.
Journal of Medical Genetics, 2011
Background Congenital deletions affecting 3q11q23 have rarely been reported and only five cases h... more Background Congenital deletions affecting 3q11q23 have rarely been reported and only five cases have been molecularly characterised. Genotype-phenotype correlation has been hampered by the variable sizes and breakpoints of the deletions. In this study, 14 novel patients with deletions in 3q11q23 were investigated and compared with 13 previously reported patients. Methods Clinical data were collected from 14 novel patients that had been investigated by high resolution microarray techniques. Molecular investigation and updated clinical information of one cytogenetically previously reported patient were also included. The molecular investigation identified deletions in the region 3q12.3q21.3 with different boundaries and variable sizes. The smallest studied deletion was 580 kb, located in 3q13.31. Genotype-phenotype comparison in 24 patients sharing this shortest region of overlapping deletion revealed several common major characteristics including significant developmental delay, muscular hypotonia, a high arched palate, and recognisable facial features including a short philtrum and protruding lips. Abnormal genitalia were found in the majority of males, several having micropenis. Finally, a postnatal growth pattern above the mean was apparent. The 580 kb deleted region includes five RefSeq genes and two of them are strong candidate genes for the developmental delay: DRD3 and ZBTB20. Conclusion A newly recognised 3q13.31 microdeletion syndrome is delineated which is of diagnostic and prognostic value. Furthermore, two genes are suggested to be responsible for the main phenotype.
Journal of Medical Genetics, 1999
Two unrelated mildly retarded males with inversions of the X chromosome and nonspecific mental re... more Two unrelated mildly retarded males with inversions of the X chromosome and nonspecific mental retardation (MRX) are described. Case 1 has a pericentric inversion 46,Y,inv(X)(p11.1q13.1) and case 2 a paracentric inversion 46,Y,inv(X) (q13.1q28). Both male patients have severe learning diYculties. The same chromosomal abnormalities were found in their mothers who are intellectually normal. Fluorescence in situ hybridisation mapping showed a common area of breakage of each of the inverted chromosomes in Xq13.1 near DXS131 and DXS162. A detailed long range restriction map of the breakpoint region was constructed using YAC, PAC, and cosmid clones. We show that the two inverted chromosomes break within a short 250 kb region. Moreover, a group of ESTs corresponding to an as yet uncharacterised gene was mapped to the same critical interval. We hypothesise that the common inversion breakpoint region of the two cases in Xq13.1 may contain a new MRX gene.
Journal of Medical Genetics, 2010
Background Genome-wide screening of large patient cohorts with mental retardation using microarra... more Background Genome-wide screening of large patient cohorts with mental retardation using microarray-based comparative genomic hybridisation (array-CGH) has recently led to identification several novel microdeletion and microduplication syndromes. Methods Owing to the national array-CGH network funded by the French Ministry of Health, shared information about patients with rare disease helped to define critical intervals and evaluate their gene content, and finally determine the phenotypic consequences of genomic array findings. Results In this study, nine unrelated patients with overlapping de novo interstitial microdeletions involving 4q21 are reported. Several major features are common to all patients, including neonatal muscular hypotonia, severe psychomotor retardation, marked progressive growth restriction, distinctive facial features and absent or severely delayed speech. The boundaries and the sizes of the nine deletions are different, but an overlapping region of 1.37 Mb is defined; this region contains five RefSeq genes: PRKG2, RASGEF1B, HNRNPD, HNRPDL and ENOPH1. Discussion Adding new individuals with similar clinical features and 4q21 deletion allowed us to reduce the critical genomic region encompassing two genes, PRKG2 and RASGEF1B. PRKG2 encodes cGMP-dependent protein kinase type II, which is expressed in brain and in cartilage. Information from genetically modified animal models is pertinent to the clinical phenotype. RASGEF1B is a guanine nucleotide exchange factor for Ras family proteins, and several members have been reported as key regulators of actin and microtubule dynamics during both dendrite and spine structural plasticity. Conclusion Clinical and molecular delineation of 4q21 deletion supports a novel microdeletion syndrome and suggests a major contribution of PRKG2 and RASGEF1B haploinsufficiency to the core phenotype.
Journal of Experimental Medicine, 2013
DNA double strand breaks (DSBs) are mainly repaired via homologous recombination (HR) or nonhomol... more DNA double strand breaks (DSBs) are mainly repaired via homologous recombination (HR) or nonhomologous end joining (NHEJ). These breaks pose severe threats to genome integrity but can also be necessary intermediates of normal cellular processes such as immunoglobulin class switch recombination (CSR). During CSR, DSBs are produced in the G1 phase of the cell cycle and are repaired by the classical NHEJ machinery. By studying B lymphocytes derived from patients with Cornelia de Lange Syndrome, we observed a strong correlation between heterozygous loss-of-function mutations in the gene encoding the cohesin loading protein NIPBL and a shift toward the use of an alternative, microhomology-based end joining during CSR. Furthermore, the early recruitment of 53BP1 to DSBs was reduced in the NIPBL-deficient patient cells. Association of NIPBL deficiency and impaired NHEJ was also observed in a plasmid-based end-joining assay and a yeast model system. Our results suggest that NIPBL plays an i...
Human Mutation, 2007
Cornelia de Lange syndrome (CdLS) is a multisystem developmental disorder characterized by facial... more Cornelia de Lange syndrome (CdLS) is a multisystem developmental disorder characterized by facial dysmorphism, growth and mental retardation, microcephaly, and various malformations. Heterozygous mutations in the NIPBL gene have been detected in approximately 45% of affected individuals. Recently, a second CdLS gene, mapping to the X chromosome, has been identified: SMC1L1 (structural maintenance of chromosomes 1-like 1; or SMC1A). In order to estimate the incidence and refine the clinical presentation of Xlinked CdLS, we have screened a series of 11 CdLS boys carrying no NIPBL anomaly. We have identified two novel de novo SMC1L1 missense mutations (c.587G>A [p.Arg196His] and c.3254A>G [p.Tyr1085Cys]). Our results confirm that SMC1L1 mutations cause CdLS and support the view that SMC1L1 accounts for a significant fraction of boys with unexplained CdLS. Furthermore, we suggest that SMC1L1 mutations have milder effects than NIPBL mutations with respect to pre-and postnatal growth retardation and associated malformations. If confirmed, these data may have important implications for directing mutation screening in CdLS.
Human Molecular Genetics, 2013
European Journal of Human Genetics, 2009
X-linked mental retardation is a common disorder that accounts for 5-10% of cases of mental retar... more X-linked mental retardation is a common disorder that accounts for 5-10% of cases of mental retardation in males. Fragile X syndrome is the most common form resulting from a loss of expression of the FMR1 gene. On the other hand, partial duplication of the long arm of the X chromosome is uncommon. It leads to functional disomy of the corresponding genes and has been reported in several cases of mental retardation in males. In this study, we report on the clinical and genetic characterization of a new X-linked mental retardation syndrome characterized by short stature, hypogonadism and facial dysmorphism, and show that this syndrome is caused by a small Xq27.3q28 interstitial duplication encompassing the FMR1 gene. This family broadens the phenotypic spectrum of FMR1 anomalies in an unexpected manner, and we suggest that this condition may represent the fragile X syndrome )contre-type*.
European Journal of Human Genetics, 2006
In the course of a systematic whole genome screening of patients with unexplained overgrowth synd... more In the course of a systematic whole genome screening of patients with unexplained overgrowth syndrome by microarray-based comparative genomic hybridisation (array-CGH), we have identified two children with nearly identical 6.5 Mb-long de novo interstitial deletions at 9q22.32 -q22.33. The clinical phenotype includes macrocephaly, overgrowth and trigonocephaly. In addition, both children present with psychomotor delay, hyperactivity and distinctive facial features. Further analysis with a high-resolution custom microarray covering the whole breakpoint intervals with fosmids mapped the deletion breakpoints within 100-kb intervals: although the deletion boundaries are different for the two patients, nearly the same genes are deleted in both cases. We suggest therefore that microdeletion of 9q22.32-q22.33 is a novel cause of overgrowth and mental retardation. Its association with distinctive facial features should help in recognising this novel phenotype.
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Papers by Laurence Colleaux