Comprehensive mutational analysis of a cohort of Swedish Cornelia de Lange syndrome patients

A Novel de Novo Variant in 5' UTR of the NIPBL Associated with Cornelia de Lange Syndrome

Background: Cornelia de Lange syndrome (CdLS) is a genetic syndrome characterized by intellectual disability, special facial features, growth retardation, feeding difficulties, and multiple organ system abnormalities. NIPBL variants occur in approximately 80% of CdLS cases. Aims: We report a novel de novo heterozygous pathogenic variant in the NIPBL and its association with CdLS. We also examined the key regulatory sequences of the 5′ untranslated region in NIPBL mRNA. Few studies have reported mutation sites in the 5′ untranslated region (UTR) of the NIPBL that result in CdLS. Methods: The patient’s medical history, clinical manifestations, physical examination, laboratory examination, Griffiths development assessment scale—Chinese version, and cardiac B-ultrasound were examined. Mutation screening was conducted using trio whole exome sequencing (trio-WES) and Sanger sequencing. Quantitative PCR was performed to measure the NIPBL expression in peripheral blood mononuclear cells. A Dual-Luciferase reporter assay was conducted to evaluate the transcription of truncated mutants. Results: The proband showed characteristics of CdLS including thick eyebrows, a concave nasal ridge, long and smooth philtrum, downturned corners of the mouth, intellectual disability, postnatal growth retardation, and a short fifth toe. A novel de novo heterozygous pathogenic variant in the NIPBL (c.-467C > T) was identified. A Dual-Luciferase reporter gene assay showed that SPO1 (-490 bp to -360 bp) and SPO3 (-490 bp to -401 bp) induced the highest activity. Conclusions: We found a novel de novo heterozygous pathogenic variant (c.-467C > T) in the NIPBL resulting in CdLS. Our findings expand the spectrum of pathogenic mutations for CdLS. Our in vitro experiments elucidated important regulatory sequences in the 5′ UTR of the NIPBL.

A Broader Perspective on the Prenatal Diagnosis of Cornelia de Lange Syndrome: Review of the Literature and Case Presentation

Cornelia de Lange syndrome (CDLS) is caused by pathogenic variants in genes which are structural or regulatory components of the cohesin complex. The classical Cornelia de Lange (CDLS) phenotype is characterized by distinctive facial features, growth retardation, upper limb reduction defects, hirsutism, and developmental delay. Non-classical phenotypes make this condition heterogeneous. Although CDLS is a heterogeneous clinical and genetic condition, clear diagnostic criteria have been described by specialist consensus. Many of these criteria refer to features that can be seen on prenatal ultrasound. The aim of this paper is twofold: to present the ultrasound findings in fetuses affected by CDLS syndrome; to discuss the recent advances and the limitations in the ultrasound and genetic prenatal diagnosis of CDLS. Our review aims to offer, apart from the data needed to understand the genetics and the prenatal presentation of the disease, a joint perspective of the two specialists involved in the prenatal management of this pathology: the fetal medicine specialist and the geneticist. To better illustrate the data presented, we also include a representative clinical case.

De novo NIPBL Mutations in Vietnamese Patients with Cornelia de Lange Syndrome

Cornelia de Lange Syndrome (CdLS) is a rare congenital genetic disease causing abnormal unique facial phenotypes, several defects in organs and body parts, and mental disorder or intellectual disorder traits. Main causes of CdLS have been reported as variants in cohesin complex genes, in which mutations in the NIPBL gene have been estimated to account for up to 80%. Our study included three Vietnamese patients with typical CdLS phenotypes. Whole exome sequencing revealed two known heterozygous mutations c.6697G>A (p.Val2233Met) and c.2602C>T (p.Arg868X), and a novel heterozygous mutation c.4504delG (p.Val1502fsX87) in the NIPBL gene of the three patients. In silico analyses of the identified mutations predicted possible damaging and truncating effects on the NIPBL protein. Inherited analyses in the patients' families showed that all of the mutations are de novo. Our results lead a definitive diagnosis of patients with CdLS and expand the spectrum of mutations in the NIPBL gene. These findings also confirm whole exome sequencing is an efficient tool for genetic screening of CdLS.

Branding of subjects affected with genetic syndromes of severe short stature in developing countries

In Ecuador, a developing South American country, subjects affected with genetic syndromes of severe short stature are commonly referred to as dwarfs or midgets. Furthermore, and because in earlier studies some patients had evidenced mental retardation, such abnormality is assumed to exist in all affected subjects. Herein, we present two discrete instances in which this type of branding occurs. The first is that of individuals with Laron syndrome who are still called 'dwarfs' and considered as having a degree of mental retardation despite evidence showing otherwise. A similar problem, that of a girl affected with a genetic syndrome of short stature, which might include mental retardation, is also discussed. Considering that stigmatising is a form of discrimination, it concerns us all. Hence, the use of derogatory terms such as midget, dwarf or cretin, that might unintentionally occur even when delivering the best and most devoted medical care, must be eliminated.

Clinical and genetic study of 20 patients from China with Cornelia de Lange syndrome

Background

Cornelia de Lange syndrome (CdLS) is a rare congenital syndrome with no racial difference. The objective of this study is to report the clinical characteristics and genetic study of 20 CdLS cases from China.

Methods

This is an observational study. Suspected patients were referred for further confirmation, clinical treatment, and genetic testing under voluntary condition. Demographic data and family history, data of clinical manifestations including facial dysmorphism and developmental delay of each patient were collected. Chromosomal analysis and NIPBL/SMC1A/SMC3 gene mutational analysis were carried out by PCR, reverse transcription PCR direct sequencing in the probands, and SNP array to detect the genome-wide copy number variations.

Results

Twenty CdLS cases from China were included in this study. Facial dysmorphisms, feeding difficulties, and developmental delay were the major clinical manifestations. Seven patients underwent gene mutation tests. Both the SMC1A and SMC3 gene mutation tests were negative in all. A heterozygous mutation in exon 20 of the NIPBL gene in proband 2, and a heterozygous mutation in intron 38 of the NIPBL gene in proband 3 were found in 1 patient, and RT-PCR revealed a splicing mutation in exon 38, generating both normal transcript and an aberrant alternatively spliced transcript with exon 38 deletion.

Conclusions

Clinical manifestations of CdLS patients from China are similar to those in the other countries. Heterozygous mutations of NIPBL gene were found.

A new prognostic index of severity of intellectual disabilities in Cornelia de Lange syndrome

Cornelia de Lange syndrome is a well-known multiple congenital anomalies/intellectual disability syndrome with genetic heterogeneity and wide clinical variability, regarding the severity of both the intellectual disabilities and the physical features, not completely explained by the genotype-phenotype correlations known to date. The aim of the study was the identification of prognostic features, ascertainable precociously in the patient's life, of a better intellectual outcome and the development of a new prognostic index of severity of intellectual disability in CdLS patients. In 66 italian CdLS patients aged 8 years or more, we evaluated the association of the degree of intellectual disability with various clinical parameters ascertainable before 6 months of life and with the molecular data by the application of cumulative regression logistic model. Based on these results and on the previously known genotype-phenotype correlations, we selected seven parameters to be used in a multivariate cumulative regression logistic model to develop a prognostic index of severity of intellectual disability. The probability of a mild ID increases with the reducing final score less than two, the probability of a severe ID increases with the increasing final score more than three. This prognostic index allows to define, precociously in the life of a baby, the probability of a better or worse intellectual outcome in CdLS patients. © 2016 Wiley Periodicals, Inc.

Cornelia de Lange and Ehlers-Danlos: comorbidity of two rare syndromes

We present a case of a young adult with both Cornelia de Lange syndrome and Ehlers-Danlos syndrome. The patient showed non-verbal autism, intellectual disability and severe/intractable self-harming behaviours that led to a life-threatening complication (ie, septicaemia). A significant reduction in the self-harming behaviours was attained in a multidisciplinary neurobehavioural inpatient unit after addressing all causes of somatic pains, managing pain using level II and III analgesics, stabilising the patient's mood, limiting the iatrogenic effects of multiple prescriptions and offering a specific psychoeducational approach.

Functional characterization of NIPBL physiological splice variants and eight splicing mutations in patients with Cornelia de Lange syndrome

Cornelia de Lange syndrome (CdLS) is a congenital developmental disorder characterized by distinctive craniofacial features, growth retardation, cognitive impairment, limb defects, hirsutism, and multisystem involvement. Mutations in five genes encoding structural components (SMC1A, SMC3, RAD21) or functionally associated factors (NIPBL, HDAC8) of the cohesin complex have been found in patients with CdLS. In about 60% of the patients, mutations in NIPBL could be identified. Interestingly, 17% of them are predicted to change normal splicing, however, detailed molecular investigations are often missing. Here, we report the first systematic study of the physiological splicing of the NIPBL gene, that would reveal the identification of four new splicing isoforms ΔE10, ΔE12, ΔE33,34, and B’. Furthermore, we have investigated nine mutations affecting splice-sites in the NIPBL gene identified in twelve CdLS patients. All mutations have been examined on the DNA and RNA level, as well as by in silico analyses. Although patients with mutations affecting NIPBL splicing show a broad clinical variability, the more severe phenotypes seem to be associated with aberrant transcripts resulting in a shift of the reading frame.

Severe ipsilateral musculoskeletal involvement in a Cornelia de Lange patient with a novel NIPBL mutation

Cornelia de Lange Syndrome (CdLS) is a congenital autosomal dominant (NIPBL, SMC3 and RAD21) or X-linked (SMC1A and HDAC8) disorder characterized by facial dysmorphism, pre and postnatal growth retardation, developmental delay and/or intellectual disability, and multiorgan involvement. Musculoskeletal malformations are usually bilateral and affect mainly the upper limbs; the range goes from brachyclinodactyly to severe reduction defects. Instead lower extremities are usually less and mildly involved. Here, we report on a 3-year-old Senegalese boy with typical craniofacial CdLS features, pre and postnatal growth retardation, atrial septal defect, developmental delay and right ipsilateral limb malformations, consistent with oligodactyly of the 3rd and 4th fingers, tibial agenesis and fibula hypoplasia. Exome sequencing and Sanger sequencing showed a novel missense mutation in NIPBL gene (c.6647A>G; p.(Tyr2216Cys)), which affects a conserved residue located within NIPBL HEAT repeat elements. Pyrosequencing analysis of NIPBL gene, disclosed similar levels of wild-type and mutated alleles in DNA and RNA samples from all tissues analyzed (oral mucosa epithelial cells, peripheral blood leukocytes and fibroblasts). These findings indicated the absence of somatic mosaicism, despite of the segmental asymmetry of the limbs, and confirmed biallelic expression for NIPBL transcripts, respectively. Additionally, conditions like Split-hand/foot malformation with long-bone deficiency secondary to duplication of BHLHA9 gene have been ruled out by the array-CGH and MLPA analysis. To our knowledge, this is the first CdLS patient described with major ipsilateral malformations of both the upper and lower extremities, that even though this finding could be due to a random event, expands the spectrum of limb reduction defects in CdLS.

Mutation spectrum and genotype-phenotype correlation in Cornelia de Lange syndrome

Cornelia de Lange syndrome (CdLS) is a clinically and genetically heterogeneous developmental disorder. Clinical features include growth retardation, intellectual disability, limb defects, typical facial dysmorphism, and other systemic involvement. The increased understanding of the genetic basis of CdLS has led to diagnostic improvement and expansion of the phenotype. Mutations in five genes (NIPBL, SMC1A, SMC3, RAD21, and HDAC8), all regulators or structural components of cohesin, have been identified. Approximately 60% of CdLS cases are due to NIPBL mutations, 5% caused by mutations in SMC1A, RAD21, and HDAC8 and one proband was found to carry a mutation in SMC3. To date, 311 CdLS-causing mutations are known including missense, nonsense, small deletions and insertions, splice site mutations, and genomic rearrangements. Phenotypic variability is seen both intra- and intergenically. This article reviews the spectrum of CdLS mutations with a particular emphasis on their correlation to the clinical phenotype.

A regulatory role for the cohesin loader NIPBL in nonhomologous end joining during immunoglobulin class switch recombination

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 important and evolutionarily conserved role in NHEJ, in addition to its canonical function in sister chromatid cohesion and its recently suggested function in HR.

Copy number analysis of NIPBL in a cohort of 510 patients reveals rare copy number variants and a mosaic deletion

Cornelia de Lange syndrome (CdLS) is a genetically heterogeneous disorder characterized by growth retardation, intellectual disability, upper limb abnormalities, hirsutism, and characteristic facial features. In this study we explored the occurrence of intragenic NIPBL copy number variations (CNVs) in a cohort of 510 NIPBL sequence-negative patients with suspected CdLS. Copy number analysis was performed by custom exon-targeted oligonucleotide array-comparative genomic hybridization and/or MLPA. Whole-genome SNP array was used to further characterize rearrangements extending beyond the NIPBL gene. We identified NIPBL CNVs in 13 patients (2.5%) including one intragenic duplication and a deletion in mosaic state. Breakpoint sequences in two patients provided further evidence of a microhomology-mediated replicative mechanism as a potential predominant contributor to CNVs in NIPBL. Patients for whom clinical information was available share classical CdLS features including craniofacial and limb defects. Our experience in studying the frequency of NIBPL CNVs in the largest series of patients to date widens the mutational spectrum of NIPBL and emphasizes the clinical utility of performing NIPBL deletion/duplication analysis in patients with CdLS.

Genomic imbalances in patients with a clinical presentation in the spectrum of Cornelia de Lange syndrome

Background

Cornelia de Lange syndrome (CdLS) is a rare autosomal-dominant disorder characterised by facial dysmorphism, growth and psychomotor developmental delay and skeletal defects. To date, causative mutations in the NIPBL (cohesin regulator) and SMC1A (cohesin structural subunit) genes account for > 50% and 6% of cases, respectively.

Methods

We recruited 50 patients with a CdLS clinical diagnosis or with features that overlap with CdLS, who were negative for mutations at NIPBL and SMC1A at molecular screening. Chromosomal rearrangements accounting for the clinical diagnosis were screened for using array Comparative Genomic Hybridisation (aCGH).

Results

Four patients were shown to carry imbalances considered to be candidates for having pathogenic roles in their clinical phenotypes: patient 1 had a 4.2 Mb de novo deletion at chromosome 20q11.2-q12; patient 2 had a 4.8 Mb deletion at chromosome 1p36.23-36.22; patient 3 carried an unbalanced translocation, t(7;17), with a 14 Mb duplication of chromosome 17q24.2-25.3 and a 769 Kb deletion at chromosome 7p22.3; patient 4 had an 880 Kb duplication of chromosome 19p13.3, for which his mother, who had a mild phenotype, was also shown to be a mosaic.

Conclusions

Notwithstanding the variability in size and gene content of the rearrangements comprising the four different imbalances, they all map to regions containing genes encoding factors involved in cell cycle progression or genome stability. These functional similarities, also exhibited by the known CdLS genes, may explain the phenotypic overlap between the patients included in this study and CdLS. Our findings point to the complexity of the clinical diagnosis of CdLS and confirm the existence of phenocopies, caused by imbalances affecting multiple genomic regions, comprising 8% of patients included in this study, who did not have mutations at NIPBL and SMC1A. Our results suggests that analysis by aCGH should be recommended for CdLS spectrum cases with an unexplained clinical phenotype and included in the flow chart for diagnosis of cases with a clinical evaluation in the CdLS spectrum.

Spectrum of NIPBL gene mutations in Polish patients with Cornelia de Lange syndrome

Cornelia de Lange syndrome (CdLS) is a rare multi-system genetic disorder characterised by growth and developmental delay, distinctive facial dysmorphism, limb malformations and multiple organ defects. The disease is caused by mutations in genes responsible for the formation and regulation of cohesin complex. About half of the cases result from mutations in the NIPBL gene coding delangin, a protein regulating the initialisation of cohesion. To date, approximately 250 point mutations have been identified in more than 300 CdLS patients worldwide. In the present study, conducted on a group of 64 unrelated Polish CdLS patients, 25 various NIPBL sequence variants, including 22 novel point mutations, were detected. Additionally, large genomic deletions on chromosome 5p13 encompassing the NIPBL gene locus were detected in two patients with the most severe CdLS phenotype. Taken together, 42 % of patients were found to have a deleterious alteration affecting the NIPBL gene, by and large private ones (89 %). The review of the types of mutations found so far in Polish patients, their frequency and correlation with the severity of the observed phenotype shows that Polish CdLS cases do not significantly differ from other populations.

Intragenic and large NIPBL rearrangements revealed by MLPA in Cornelia de Lange patients

Cornelia de Lange syndrome (CdLS) is a rare multisystemic congenital anomaly disorder that is characterised by intellectual disability and growth retardation, congenital heart defects, intestinal anomalies, facial dysmorphism (including synophyris and high arched eyebrows) and limb reduction defects. Mutations in three cohesin-associated genes encoding a key regulator (NIPBL, chr 5p13.2) and one structural component of the cohesin ring (SMC1A, chr Xp11) occur in about 65% of CdLS patients. NIPBL is the major causative gene, and accounts for 40-60% of CdLS patients as shown by a number of mutational screening studies that indicate a wide mutational repertoire of mainly small deletions and point mutations. Only a few data are available concerning the occurrence of large NIPBL rearrangements or intragenic deletions or duplications involving whole exons. We used multiplex ligation-dependent probe amplification (MLPA) to study 132 CdLS patients negative to the standard mutation NIPBL test out of a cohort of 200 CdLS patients. A total of 7 out of 132 patients were found to carry NIPBL alterations, including two large gene deletions extending beyond the gene, four intragenic multi- or single-exon deletions and one single-exon duplication. These findings show that MLPA leads to a 5.3% increase in the detection of mutations when used in addition to the standard NIPBL scan, and contributes per se to the molecular diagnosis of 3.5% (7/200) of clinically diagnosed CdLS patients. It is recommended that MLPA be included in the CdLS diagnostic flow chart.

Isolated NIBPL missense mutations that cause Cornelia de Lange syndrome alter MAU2 interaction

Cornelia de Lange syndrome (CdLS; or Brachmann-de Lange syndrome) is a dominantly inherited congenital malformation disorder with features that include characteristic facies, cognitive delays, growth retardation and limb anomalies. Mutations in nearly 60% of CdLS patients have been identified in NIPBL, which encodes a regulator of the sister chromatid cohesion complex. NIPBL, also known as delangin, is a homolog of yeast and amphibian Scc2 and C. elegans PQN-85. Although the exact mechanism of NIPBL function in sister chromatid cohesion is unclear, in vivo yeast and C. elegans experiments and in vitro vertebrate cell experiments have demonstrated that NIPBL/Scc2 functionally interacts with the MAU2/Scc4 protein to initiate loading of cohesin onto chromatin. To test the significance of this model in the clinical setting of CdLS, we fine-mapped the NIBPL-MAU2 interaction domain and tested the functional significance of missense mutations and variants in NIPBL and MAU2 identified in these minimal domains in a cohort of patients with CdLS. We demonstrate that specific novel mutations at the N-terminus of the MAU2-interacting domain of NIBPL result in markedly reduced MAU2 binding, although we appreciate no consistent clinical difference in the small group of patients with these mutations. These data suggest that factors in addition to MAU2 are essential in determining the clinical features and severity of CdLS.

Mutations and variants in the cohesion factor genes NIPBL, SMC1A, and SMC3 in a cohort of 30 unrelated patients with Cornelia de Lange syndrome

Cornelia de Lange syndrome (CdLS) manifests facial dysmorphic features, growth and cognitive impairment, and limb malformations. Mutations in three genes (NIPBL, SMC1A, and SMC3) of the cohesin complex and its regulators have been found in affected patients. Here, we present clinical and molecular characterization of 30 unrelated patients with CdLS. Eleven patients had mutations in NIPBL (37%) and three patients had mutations in SMC1A (10%), giving an overall rate of mutations of 47%. Several patients shared the same mutation in NIPBL (p.R827GfsX2) but had variable phenotypes, indicating the influence of modifiers in CdLS. Patients with NIPBL mutations had a more severe phenotype than those with mutations in SMC1A or those without identified mutations. However, a high incidence of palate defects was noted in patients with SMC1A mutations. In addition, we observed a similar phenotype in both male and female patients with SMC1A mutations. Finally, we report the first patient with an SMC1A mutation and the Sandifer complex.

Cornelia De Lange syndrome: a case report of a Brazilian boy

Cornelia de Lange syndrome is a rare multisystem disorder characterized by a distinctive facial appearance, delayed growth and psychomotor skills, behavioral problems, malformation of the upper limbs, and impairment on the quality of life of affected subjects. This article reports a case of a child with the syndrome, emphasizing the orofacial manifestations. Knowledge on the etiopathological aspects and characteristic features of this condition is essential so that professionals can provide health care and help improve the quality of life of affected individuals and their families.

Brachmann-de Lange syndrome with congenital diaphragmatic hernia and NIPBL gene mutation

We report herein a case of Brachmann-de Lange syndrome complicated with congenital diaphragmatic hernia in which a NIPBL gene mutation was identified. A female infant born at 37 weeks of gestation died 134 min after delivery, even though endotracheal intubation and resuscitation were performed immediately after the scheduled caesarean operation. We diagnosed the infant with Brachmann-de Lange syndrome from her physical characteristics. An abnormal peak at the 29th exon in the translation area of the NIPBL gene was detected using denaturing high-performance liquid chromatography. In addition, a mutation of cytosine to thymine (nonsense mutation) at the 5524th base was identified using the direct sequence method. This variation was likely the cause of the syndrome.

A case of third trimester diagnosis of Cornelia de Lange syndrome

AIM

The objective is to present a rare case of late diagnosis of Cornelia de Lange syndrome.

CASE

A 27-year-old pregnant woman (gravida 1, para 0) was referred to our Fetal Medicine Department during her 33rd week of gestation due to intrauterine growth restriction (IUGR) and polyhydramnios. The ultrasound scanning confirmed the findings and furthermore, the 3-D examination revealed minor facial dysmorphisms, limb abnormalities, and hypertrichosis. The fetus died 1 week post-diagnosis due to unknown reason and the woman underwent an induction of labor. Postmortem examination confirmed the diagnosis of Cornelia de Lange syndrome.

CONCLUSION

The prognosis of the syndrome is severe. Termination of pregnancy before viability is proposed. Genetic counseling is necessary.

Multiple organ system defects and transcriptional dysregulation in the Nipbl(+/-) mouse, a model of Cornelia de Lange Syndrome

Cornelia de Lange Syndrome (CdLS) is a multi-organ system birth defects disorder linked, in at least half of cases, to heterozygous mutations in the NIPBL gene. In animals and fungi, orthologs of NIPBL regulate cohesin, a complex of proteins that is essential for chromosome cohesion and is also implicated in DNA repair and transcriptional regulation. Mice heterozygous for a gene-trap mutation in Nipbl were produced and exhibited defects characteristic of CdLS, including small size, craniofacial anomalies, microbrachycephaly, heart defects, hearing abnormalities, delayed bone maturation, reduced body fat, behavioral disturbances, and high mortality (75–80%) during the first weeks of life. These phenotypes arose despite a decrease in Nipbl transcript levels of only ∼30%, implying extreme sensitivity of development to small changes in Nipbl activity. Gene expression profiling demonstrated that Nipbl deficiency leads to modest but significant transcriptional dysregulation of many genes. Expression changes at the protocadherin beta (Pcdhb) locus, as well as at other loci, support the view that NIPBL influences long-range chromosomal regulatory interactions. In addition, evidence is presented that reduced expression of genes involved in adipogenic differentiation may underlie the low amounts of body fat observed both in Nipbl+/− mice and in individuals with CdLS.

Cornelia de Lange Syndrome (CdLS) is a genetic disease marked by growth retardation, cognitive and neurological problems, and structural defects in many organ systems. The majority of CdLS cases are due to mutation of one copy of the Nipped B-like (NIPBL) gene, the product of which regulates a complex of chromosomal proteins called cohesin. How reduction of NIPBL function gives rise to pervasive developmental defects in CdLS is not understood, so a model of CdLS was developed by generating mice that carry one null allele of Nipbl. Developmental defects in these mice show remarkable similarity to those observed in individuals with CdLS, including small stature, craniofacial abnormalities, reduced body fat, behavioral disturbances, and high perinatal mortality. Molecular analysis of tissues and cells from Nipbl mutant mice provide the first evidence that the major role of Nipbl in the etiology of CdLS is to exert modest, but significant, effects on the expression of diverse sets of genes, some of which are located in characteristic arrangements along the DNA. Among affected genes is a set involved in the development of adipocytes, the cells that make and accumulate body fat, potentially explaining reductions in body fat accumulation commonly observed in individuals with CdLS.

Functional links between Drosophila Nipped-B and cohesin in somatic and meiotic cells

Drosophila Nipped-B is an essential protein that has multiple functions. It facilitates expression of homeobox genes and is also required for sister chromatid cohesion. Nipped-B is conserved from yeast to man, and its orthologs also play roles in deoxyribonucleic acid repair and meiosis. Mutation of the human ortholog, Nipped-B-Like (NIPBL), causes Cornelia de Lange syndrome (CdLS), associated with multiple developmental defects. The Nipped-B protein family is required for the cohesin complex that mediates sister chromatid cohesion to bind to chromosomes. A key question, therefore, is whether the Nipped-B family regulates gene expression, meiosis, and development by controlling cohesin. To gain insights into Nipped-B's functions, we compared the effects of several Nipped-B mutations on gene expression, sister chromatid cohesion, and meiosis. We also examined association of Nipped-B and cohesin with somatic and meiotic chromosomes by immunostaining. Missense Nipped-B alleles affecting the same HEAT repeat motifs as CdLS-causing NIPBL mutations have intermediate effects on both gene expression and mitotic chromatid cohesion, linking these two functions and the role of NIPBL in human development. Nipped-B colocalizes extensively with cohesin on chromosomes in both somatic and meiotic cells and is present in soluble complexes with cohesin subunits in nuclear extracts. In meiosis, Nipped-B also colocalizes with the synaptonemal complex and contributes to maintenance of meiotic chromosome cores. These results support the idea that direct regulation of cohesin function underlies the diverse functions of Nipped-B and its orthologs.

Cohesin and human disease

Cornelia de Lange syndrome (CdLS) is a dominant multisystem disorder caused by a disruption of cohesin function. The cohesin ring complex is composed of four protein subunits and more than 25 additional proteins involved in its regulation. The discovery that this complex also has a fundamental role in long-range regulation of transcription in Drosophila has shed light on the mechanism likely responsible for its role in development. In addition to the three cohesin proteins involved in CdLS, a second multisystem, recessively inherited, developmental disorder, Roberts-SC phocomelia, is caused by mutations in another regulator of the cohesin complex, ESCO2. Here we review the phenotypes of these disorders, collectively termed cohesinopathies, as well as the mechanism by which cohesin disruption likely causes these diseases.

Clinical score of 62 Italian patients with Cornelia de Lange syndrome and correlations with the presence and type of NIPBL mutation

Cornelia de Lange syndrome (CdLS) is a rare multisystem disorder characterized by facial dysmorphisms, upper limb abnormalities, growth and cognitive retardation. About half of all patients with CdLS carry mutations in the NIPBL gene. The first Italian CdLS cohort involving 62 patients (including 4 related members) was screened for NIPBL mutations after a clinical evaluation using a quantitative score that integrates auxological, malformation and neurodevelopmental parameters. The patients were classified as having an overall 'severe', 'moderate' or 'mild' phenotype. NIPBL screening showed 26 mutations so classified: truncating (13), splice-site (8), missense (3), in-frame deletion (1) and regulatory (1). The truncating mutations were most frequently found in the patients with a high clinical score, whereas most of the splice-site and all missense mutations clustered in the low-medium score groups. The NIPBL-negative group included patients covering the entire clinical spectrum. The prevalence of a severe phenotype in the mutated group and a mild phenotype in the non-mutated group was statistically significant. In terms of the isolated clinical signs, the statistically significant differences between the mutation-positive and mutation-negative individuals were pre- and post-natal growth deficits, limb reduction, and delayed speech development. The proposed score seems to be a valuable means of prioritizing the patients with CdLS to undergo an NIPBL mutation test.

Increased DNA damage sensitivity of Cornelia de Lange syndrome cells: evidence for impaired recombinational repair

Cornelia de Lange syndrome (CdLS) is a rare dominantly inherited multisystem disorder affecting both physical and mental development. Heterozygous mutations in the NIPBL gene were found in about half of CdLS cases. Scc2, the fungal ortholog of the NIPBL gene product, is essential for establishing sister chromatid cohesion. In yeast, the absence of cohesion leads to chromosome mis-segregation and defective repair of DNA double-strand breaks. To evaluate possible DNA repair defects in CdLS cells, we characterized the cellular responses to DNA-damaging agents. We show that cells derived from CdLS patients, both with and without detectable NIPBL mutations, have an increased sensitivity for mitomycin C (MMC). Exposure of CdLS fibroblast and B-lymphoblastoid cells to MMC leads to enhanced cell killing and reduced proliferation and, in the case of primary fibroblasts, an increased number of chromosomal aberrations. After X-ray exposure increased numbers of chromosomal aberrations were also detected, but only in cells irradiated in the G(2)-phase of the cell cycle when repair of double-strand breaks is dependent on the establishment of sister chromatid cohesion. Repair at the G(1) stage is not affected in CdLS cells. Our studies indicate that CdLS cells have a reduced capacity to tolerate DNA damage, presumably as a result of reduced DNA repair through homologous recombination.