1q32-q41 microdeletion with reference to Van der Woude syndrome and allied clefting entities

Microdeletion of the entire IRF6 gene in a Subsaharian African's family with Van der Woude syndrome

Microdeletion of the entire interferon regulatory factory 6 (IRF 6) gene is a rare cause of Van der Woude syndrome (VDW) with only few cases reported in medical literature. Its occurrence in multiple affected members of a family is exceptional. The aim of this presentation was to describe a Central African family with typical VDW phenotype carrying an IRF6 gene deletion. Here we reported phenotype features of members of a Central African family with VDW syndrome consisting of labioalveolar cleft, depressions of the lower lip with labial fistulae (lip pits), submucosal clefts and cleft palate. Mutation analysis by means of multiplex ligation-dependent probe amplification and chromosomal microarray revealed a 374.070 kb, deletion encompassing the entire IRF6 gene in four affected family members. Microdeletion of the entire IRF6 gene causes the classical VDW syndrome phenotype.

[Van der Woude syndrome: An unrecognised clinical entity]

Van der Woude syndrome is known to be the first syndromic cause of oral cleft. Apart clefts the cardinal signs are lower lip pits and hypodontia. IRF6 gene mutations have been recently identified as potential cause in this syndrome which permits to better understand its phenotype heterogeneity. Based on a literature review, we tried to cover the different aspects of this syndrome with an emphasis on genetic counselling and surgical correction of lip pits.

De novo interstitial deletion of 1q32.2-q32.3 including the entire IRF6 gene in a patient with oral cleft and other dysmorphic features

BACKGROUND

Microdeletion of the Van der Woude syndrome (VWS) critical region is a relatively rare event, and only a few cases have been reported in the medical literature. The extent of the deletion and the genotype-phenotype correlation are 2 crucial issues.

METHODS AND RESULTS

During analysis of the VWS critical region in 95 families with an isolated cleft of the lip with or without cleft palate, we found a de novo interstitial deletion of 1q32.2-q32.3 in a patient with cleft lip and other dysmorphic features. The present case showed new proximal and distal end breakpoints compared to those previously reported. The results of a short tandem repeat analysis was confirmed using high resolution array-based comparative genomic hybridization and showed an interstitial deletion of approximately 2.98 Mb which involved 25 genes, including the entire IRF6 gene. Direct sequencing of the non-deleted allele of the IRF6 gene did not show any mutation, which supports a haploinsufficiency mechanism of the IRF6 gene in the development of the oral cleft.

CONCLUSION

The present report adds to the collective knowledge that oral cleft is a major clinical feature of the 1q32.2-q32.3 deletion.

Nonsyndromic cleft lip and palate: four chromosomal regions of interest

Nonsyndromic cleft lip with or without cleft palate (NSCLP), a common birth defect affecting 1/700 live births and 4,000 newborns/year in the United States, is associated with short and long-term morbidity. As such, it has significant impact on the health care system. NSCLP is a complex disorder that results from the interaction of genetic and environmental factors that are slowly being defined. Genomic scans have suggested a number of regions that may contain NSCLP loci. In this study, we have evaluated regions identified by a previously published genomic scan of affected sib-pairs and have found evidence of association in sixty-five multiplex families for eight chromosomal regions. Four of these regions, 2q37, 11p12-14, 12q13, and 16p13, have also been identified in second genomic scan of multiplex families from China. One region, defined by D11S1392, gave evidence suggesting the presence of an NSCLP locus in all three studies. Altogether, these results suggest chromosomal regions that should be targeted in order to identify NSCLP loci.

Association of chromosomal regions 3p21.2, 10p13, and 16p13.3 with nonsyndromic cleft lip and palate

Approximately 4,000 babies with nonsyndromic cleft lip with or without cleft palate (NSCLP) are born each year in the United States. Because NSCLP exhibits both etiologic and genetic heterogeneity, attempts to identify the underlying genetic causes have met with limited success and the pursuit of early promising findings have yielded mixed results. Two recent genomic scans identified a number of suggestive regions; some of these results have been supported by our lab and others in subsequent studies. Using our NSCLP multiplex family population, we were able to provide additional supportive evidence for association to the regions 2q37, 11p12-14, 12q13, and 16p13.11-p12 that were identified in the genomic scans. However, there remains a number of additional viable candidate genes and regions that have not been sufficiently investigated. These include chromosomal translocations in patients with NSCLP, growth factor genes, metalloproteinase (MMP) and transcription factor (patterning) genes, including those in the WNT family. Here, we present results from screening the 10p13 chromosomal translocation region associated with NSCLP, MMP genes clustered on chromosomes 1p36, 11q22.3, 16p13.3, and 16q12-13, and the region containing the WNT5A gene on chromosome 3p21. Markers from three of the regions, 10p13, 16p13.3 (MMP25), and 3p21.2, yielded findings that are sufficiently significant to warrant closer investigation.

Novel IRF6 mutations in Japanese patients with Van der Woude syndrome: two missense mutations (R45Q and P396S) and a 17-kb deletion

Three Japanese families with Van der Woude syndrome (VWS) were screened for mutations in the interferon regulatory factor 6 gene (IRF6) by sequencing its entire coding region. Two novel missense mutations, R45Q in exon 3 and P396S in exon 9, were identified in families 1 and 2, respectively. In family 3, no causative base change was found by the sequencing analysis, but a deletion involving exons 4-9 was suggested by multiplex PCR analysis. To confirm the deletion and to determine its 5'- and 3'-boundaries, we amplified a DNA fragment containing a heterozygous polymorphic site in exon 2 by using a 5'-upstream forward PCR primer and eight different reverse primers located 3'-downstream of exon 2. The amplified product was subjected to nested PCR to generate a DNA fragment containing the polymorphic site. When a reverse primer located within the deletion was used for the first PCR amplification, only the nondeletion allele was detected after the second PCR. Repeated analyses with eight different reverse primers allowed us to map the boundaries of the deletion, and subsequently a heterozygous 17,162-bp deletion involving exons 4-9 was identified. Since IRF6 mutations in a significant portion of VWS patients remain undetected by conventional sequencing analysis, it may be important to search for a large deletion in those patients. Our simple methods to identify deletions and to determine the boundaries of a deletion would facilitate the identification of such patients.

Van der Woude syndrome with sensorineural hearing loss, large craniofacial sinuses, dental pulp stones, and minor limb anomalies: report of a four-generation Thai family

A four-generation Thai family affected with Van der Woude syndrome is reported. The disorder appeared to be originally inherited from a person who was half Thai and half Pakistani. The lip lesions found in this family were varied and did not appear to be related to other phenotypes. There were some clinical manifestations possibly specific for the condition in this family. They included sensorineural hearing loss, prominent frontal bone, large frontal/sphenoidal/maxillary sinuses with increased mastoid air cells, long tooth roots, dental pulp stones, ankyloglossia, brachydactyly of hands, brachyphalangy, and hyperphalangy of toes, and single flexion crease of the fifth fingers. Fluorescence in situ hybridization analysis revealed no visible deletion at a 1q32-41 region.

The 6p deletion syndrome: a new orofacial clefting syndrome and its implications for antenatal screening

Foetal genetic screening has become the centre of the ethical debate surrounding the screening of foetuses for chromosomal defects to help create 'eugenic' children with either perceived advantageous characteristics or traits that could be used to medically aid unhealthy siblings. This report highlights the problems facing the medical establishment by citing, by way of example, a case of a genetic abnormality producing a clefting syndrome. The 6p deletion syndrome was first described almost 20 years ago, and the evidence is mounting for its inclusion as an orofacial clefting syndrome. This case report includes a description of the syndrome, the method used for detecting chromosomal aberrations and a comparison with other reports of the syndrome published to date. However, by pursuing a genetic-testing policy at our unit to detect new abnormalities or to help substantiate previously reported abnormalities, the way could be left open for its subsequent abuse by parents and corporations alike, so having implications not only for the individual but also for the unit performing the test. A brief synopsis is therefore also provided regarding the current circumstances of foetal screening in the UK.

Possible relationship between the van der Woude syndrome (vWS) locus and nonsyndromic cleft lip with or without cleft palate (NSCL/P)

Cleft lip with or without cleft palate (CL/P) is one of the most common congenital malformations in humans occurring with a birth prevalence of approximately 1:1,000. CL/P may be part of a defined syndrome, sequence or association, although most individual or familial cases present as an isolated (nonsyndromic) malformation (NSCL/P). Inheritance is generally regarded as multigenic although, in some families, NSCL/P seemingly segregates as a monogenic trait. On the other hand, van der Woude syndrome (vWS) is a rare autosomal dominant with cardinal features of lower-lip pits (LLP) and CL/P or cleft palate (alone). Since none of these traits is present in all mutation carriers, some individual or familial vWS cases, especially those lacking LLP, are indiscernible from NSCL/P, raising the question whether allelic variation at the vWS locus could underlie NSCL/P. This question was addressed using parametric linkage (LOD score) analysis in 21 multiplex NSCL/P families based on a tightly linked microsatellite marker (D1S3753), and nonparametric analysis using the transmission/disequilibrium test (GTDT) in 106 NSCL/P triads and selecting markers D1S205, D1S491, and D1S3753. No evidence for linkage of NSCL/P to vWS was found on the 21 families using the LOD score approach. In contrast, TDT yielded a significant P value of 0.04 for D1S205, supporting involvement of vWS in NSCL/P in a complex, modifying/polygenic manner rather than as a monogenic/major disease locus.