No abstract

Orofacial clefts (OFCs) are congenital dysmorphologies of the human face and oral cavity, with a global incidence of 1 per 700 live births. These anomalies exhibit a multifactorial pattern of inheritance, with genetic and environmental factors both playing crucial roles. Many loci have been implicated in the etiology of nonsyndromic cleft lip with or without cleft palate (NSCL/P) in populations of Asian and European ancestries, through genome-wide association studies and candidate gene studies. However, few populations of African descent have been studied to date. Here, the authors show evidence of an association of some loci with NSCL/P and nonsyndromic cleft palate only (NSCPO) in cohorts from Africa (Ghana, Ethiopia, and Nigeria). The authors genotyped 48 single-nucleotide polymorphisms that were selected from previous genome-wide association studies and candidate gene studies. These markers were successfully genotyped on 701 NSCL/P and 163 NSCPO cases, 1,070 unaffected relatives, and 1,078 unrelated controls. The authors also directly sequenced 7 genes in 184 nonsyndromic OFC (NSOFC) cases and 96 controls from Ghana. Population-specific associations were observed in the casecontrol analyses of the subpopulations, with West African subpopulations (Ghana and Nigeria) showing a similar pattern of associations. In meta-analyses of the case-control cohort, PAX7 (rs742071, P = 5.10 × 10 -3 ), 8q24 (rs987525, P = 1.22 × 10 -3 ), and VAX1 (rs7078160, P = 0.04) were nominally associated with NSCL/P, and MSX1 (rs115200552, P = 0.01), TULP4 (rs651333, P = 0.04), CRISPLD2 (rs4783099, P = 0.02), and NOG1 (rs17760296, P = 0.04) were nominally associated with NSCPO. Moreover, 7 loci exhibited evidence of threshold overtransmission in NSOFC cases through the transmission disequilibrium test and through analyses of the family-based association for disease traits. Through DNA sequencing, the authors also identified 2 novel, rare, potentially pathogenic variants (p.Asn323Asp and p.Lys426IlefsTer6) in ARHGAP29. In conclusion, the authors have shown evidence for the association of many loci with NSCL/P and NSCPO. To the best of this knowledge, this study is the first to demonstrate any of these association signals in any African population.

In African studies on salivary gland tumours, there are considerable epidemiological differences in different parts of the continent. There is no study of salivary gland tumours from the second largest hospital in Ghana, Komfo Anokye Teaching Hospital. Aim: This study was to look at the prevalence and demographic distribution of salivary gland tumours at the Komfo Anokye Teaching Hospital (KATH). Method: Histopathologically diagnosed salivary gland tumours of consecutive patients were evaluated. The study duration was from 1999 to 2010 October. Result: The total number of salivary gland tumours were 121. Male to female ratio was 1.75:1. Out of the total of 34 salivary malignancies seen, male to female ratio was 1.8:1. Malignant tumour was 28.1% while 71.9% were benign. Mean age for malignancy was 53.5 years (SD = 9.7) and that for benign was 35.5 years (SD = 8.2). Conclusion: The commonest benign tumour of the parotid was Pleomorphic adenoma (48.3%) which is consistent with most of the African and western reports. Warthin’s tumour prevalence was higher than most of the studies from Africa.

BackgroundOrofacial clefts are congenital malformations of the orofacial region, with a global incidence of one per 700 live births. Interferon Regulatory Factor 6 (IRF6) (OMIM:607199) gene has been associated with the etiology of both syndromic and nonsyndromic orofacial clefts. The aim of this study was to show evidence of potentially pathogenic variants in IRF6 in orofacial clefts cohorts from Africa.MethodsWe carried out Sanger Sequencing on DNA from 184 patients with nonsyndromic orofacial clefts and 80 individuals with multiple congenital anomalies that presented with orofacial clefts. We sequenced all the nine exons of IRF6 as well as the 5′ and 3′ untranslated regions. In our analyses pipeline, we used various bioinformatics tools to detect and describe the potentially etiologic variants.ResultsWe observed that potentially etiologic exonic and splice site variants were nonrandomly distributed among the nine exons of IRF6, with 92% of these variants occurring in exons 4 and 7. Novel variants were also observed in both nonsyndromic orofacial clefts (p.Glu69Lys, p.Asn185Thr, c.175‐2A>C and c.1060+26C>T) and multiple congenital anomalies (p.Gly65Val, p.Lys320Asn and c.379+1G>T) patients. Our data also show evidence of compound heterozygotes that may modify phenotypes that emanate from IRF6 variants.ConclusionsThis study demonstrates that exons 4 and 7 of IRF6 are mutational ‘hotspots’ in our cohort and that IRF6 mutants‐induced orofacial clefts may be prevalent in the Africa population, however, with variable penetrance and expressivity. These observations are relevant for detection of high‐risk families as well as genetic counseling. In conclusion, we have shown that there may be a need to combine both molecular and clinical evidence in the grouping of orofacial clefts into syndromic and nonsyndromic forms.

The majority (85%) of nonsyndromic cleft lip with or without cleft palate (nsCL/P) cases occur sporadically, suggesting a role for de novo mutations (DNMs) in the etiology of nsCL/P. To identify high impact protein-altering DNMs that contribute to the risk of nsCL/P, we conducted whole-genome sequencing (WGS) analyses in 130 African case-parent trios (affected probands and unaffected parents). We identified 162 high confidence protein-altering DNMs some of which are based on available evidence, contribute to the risk of nsCL/P. These include novel protein-truncating DNMs in the ACTL6A, ARHGAP10, MINK1, TMEM5 and TTN genes; as well as missense variants in ACAN, DHRS3, DLX6, EPHB2, FKBP10, KMT2D, RECQL4, SEMA3C, SEMA4D, SHH, TP63, and TULP4. Many of these protein-altering DNMs were predicted to be pathogenic. Analysis using mouse transcriptomics data showed that some of these genes are expressed during the development of primary and secondary palate. Gene-set enrichment analysis of the protein-altering DNMs identified palatal development and neural crest migration among the few processes that were significantly enriched. These processes are directly involved in the etiopathogenesis of clefting. The analysis of the coding sequence in the WGS data provides more evidence of the opportunity for novel findings in the African genome.

Background The development of the face occurs during the early days of intrauterine life by the formation of facial processes from the first Pharyngeal arch. Derangement in these well‐organized fusion events results in Orofacial clefts (OFC). Van der Woude syndrome (VWS) is one of the most common causes of syndromic cleft lip and/or palate accounting for 2% of all cases. Mutations in the IRF6 gene account for 70% of cases with the majority of these mutations located in the DNA‐binding (exon 3, 4) or protein‐binding domains (exon 7–9). The current study was designed to update the list of IRF6 variants reported for VWS by compiling all the published mutations from 2013 to date as well as including the previously unreported VWS cases from Africa and Puerto Rico. Methods We used PubMed with the search terms; "Van der Woude syndrome," “Popliteal pterygium syndrome,” "IRF6," and "Orofacial cleft" to identify eligible studies. We compiled the CADD score for all the mutations to determine the percentage of deleterious variants. Results Twenty‐one new mutations were identified from nine papers. The majority of these mutations were in exon 4. Mutations in exon 3 and 4 had CADD scores between 20 and 30 and mutations in exon 7–9 had CADD scores between 30 and 40. The presence of higher CADD scores in the protein‐binding domain (exon 7–9) further confirms the crucial role played by this domain in the function of IRF6. In the new cases, we identified five IRF6 mutations, three novel missense mutations (p.Phe36Tyr, p.Lys109Thr, and p.Gln438Leu), and two previously reported nonsense mutations (p.Ser424*and p.Arg250*). Conclusion Mutations in the protein and DNA‐binding domains of IRF6 ranked among the top 0.1% and 1% most deleterious genetic mutations, respectively. Overall, these findings expand the range of VWS mutations and are important for diagnostic and counseling purposes.

Objective Cleft lip and/or cleft palate (CL/P) are congenital anomalies of the face and have multifactorial etiology, with both environmental and genetic risk factors playing crucial roles. Though at least 40 loci have attained genomewide significant association with nonsyndromic CL/P, these loci largely reside in noncoding regions of the human genome, and subsequent resequencing studies of neighboring candidate genes have revealed only a limited number of etiologic coding variants. The present study was conducted to identify etiologic coding variants in GREM1, a locus that has been shown to be largely associated with cleft of both lip and soft palate. Patients and Method We resequenced DNA from 397 sub-Saharan Africans with CL/P and 192 controls using Sanger sequencing. Following analyses of the sequence data, we observed 2 novel coding variants in GREM1. These variants were not found in the 192 African controls and have never been previously reported in any public genetic variant database that includes more than 5000 combined African and African American controls or from the CL/P literature. Results The novel variants include p.Pro164Ser in an individual with soft palate cleft only and p.Gly61Asp in an individual with bilateral cleft lip and palate. The proband with the p.Gly61Asp GREM1 variant is a van der Woude (VWS) case who also has an etiologic variant in IRF6 gene. Conclusion Our study demonstrated that there is low number of etiologic coding variants in GREM1, confirming earlier suggestions that variants in regulatory elements may largely account for the association between this locus and CL/P.

Novel or rare damaging mutations have been implicated in the developmental pathogenesis of nonsyndromic cleft lip with or without cleft palate (nsCL ± P). Thus, we investigated the human genome for high-impact mutations that could explain the risk of nsCL ± P in our cohorts. We conducted next-generation sequencing (NGS) analysis of 130 nsCL ± P case-parent African trios to identify pathogenic variants that contribute to the risk of clefting. We replicated this analysis using whole-exome sequence data from a Brazilian nsCL ± P cohort. Computational analyses were then used to predict the mechanism by which these variants could result in increased risks for nsCL ± P. We discovered damaging mutations within the AFDN gene, a cell adhesion molecule (CAMs) that was previously shown to contribute to cleft palate in mice. These mutations include p.Met1164Ile, p.Thr453Asn, p.Pro1638Ala, p.Arg669Gln, p.Ala1717Val, and p.Arg1596His. We also discovered a novel splicing p.Leu1588Leu mutation in this protein. Computational analysis suggests that these amino acid changes affect the interactions with other cleft-associated genes including nectins (PVRL1, PVRL2, PVRL3, and PVRL4) CDH1, CTNNA1, and CTNND1. This is the first report on the contribution of AFDN to the risk for nsCL ± P in humans. AFDN encodes AFADIN, an important CAM that forms calcium-independent complexes with nectins 1 and 4 (encoded by the genes PVRL1 and PVRL4). This discovery shows the power of NGS analysis of multiethnic cleft samples in combination with a computational approach in the understanding of the pathogenesis of nsCL ± P.