Short anagen hair syndrome: association with mono- and biallelic variants in WNT10A and a genetic overlap with male pattern hair loss.

BACKGROUND: Short anagen hair (SAH) is a rare paediatric hair disorder characterized by a short anagen phase, an inability to grow long scalp hair and a negative psychological impact. The genetic basis of SAH is currently unknown. OBJECTIVES: To perform molecular genetic investigations in 48 individuals with a clinical phenotype suggestive of SAH to identify, if any, the genetic basis of this condition. METHODS: Exome sequencing was performed in 27 patients diagnosed with SAH or with a complaint of short, nongrowing hair. The cohort was screened for variants with a minor allele frequency (MAF) < 5% in the general population and a Combined Annotation Dependent Depletion (CADD) score > 15, to identify genes whose variants were enriched in this cohort. Sanger sequencing was used for variant validation and screening of 21 additional individuals with the same clinical diagnosis and their relatives. Genetic association testing of SAH-related variants for male pattern hair loss (MPHL) was performed using UK Biobank data. RESULTS: Analyses revealed that 20 individuals (42%) carried mono- or biallelic pathogenic variants in WNT10A. Rare WNT10A variants are associated with a phenotypic spectrum ranging from no clinical signs to severe ectodermal dysplasia. A significant association was found between WNT10A and SAH, and this was mostly observed in individuals with light-coloured hair and regression of the frontoparietal hairline. Notably, the most frequent variant in the cohort [c.682T>A;p.(Phe228Ile)] was in linkage disequilibrium with four common WNT10A variants, all of which have a known association with MPHL. Using UK Biobank data, our analyses showed that c.682T>A;p.(Phe228Ile) and one other variant identified in the SAH cohort are also associated with MPHL, and partially explain the known associations between WNT10A and MPHL. CONCLUSIONS: Our results suggest that WNT10A is associated with SAH and that SAH has a genetic overlap with the common phenotype MPHL. The presumed shared biologic effect of WNT10A variants in SAH and MPHL is a shortening of the anagen phase. Other factors, such as modifier genes and sex, may also play a role in the clinical manifestation of hair phenotypes associated with the WNT10A locus.

Identification of a novel mutation in RIPK4 in a kindred with phenotypic features of Bartsocas-Papas and CHAND syndromes.

Three children from an expanded consanguineous Kuwaiti kindred presented with ankyloblepharon, sparse and curly hair, and hypoplastic nails, suggestive of CHAND syndrome (OMIM 214350) that belongs to the heterogeneous spectrum of ectodermal dysplasias. After exclusion of pathogenic mutations in TP63 we performed homozygosity mapping, followed by exome sequencing of one affected individual. We initially identified three homozygous mutations in the linked region, located in PWP2, MX2 and RIPK4. Recently, mutations in RIPK4 have been reported in Bartsocas-Papas syndrome (OMIM 263650) that shows overlapping clinical symptoms with the phenotype observed in the affected individuals studied here. Subsequent analysis of affected and non-affected family members showed that mutation c.850G>A (p.Glu284Lys) in RIPK4 was in complete segregation with the disease phenotype, in accordance with an autosomal recessive inheritance pattern, thus supporting pathogenicity of this variant. Interestingly, however, our patients did not have cleft lip/palate, a common feature encountered in Bartsocas-Papas syndrome. Whereas in Bartsocas-Papas syndromes missense mutations are usually located within the serin/threonin kinase of RIPK4, the mutation detected in our family resides just outside of the kinase domain, which could explain the milder phenotype. Our data raise the question if CHAND syndrome indeed is a distinct entity. Alternatively, CHAND and Bartsocas-Papas syndrome might be allelic disorders or RIPK4 mutations could confer varying degrees of phenotypic severity, depending on their localization within or outside functionally important domains. Our findings indicate that making an accurate diagnosis based only on the prevailing clinical symptoms is challenging.

Nine novel pathogenic germline mutations in MLH1, MSH2, MSH6 and PMS2 in families with Lynch syndrome.

Many germline mutations in the DNA mismatch repair genes have been described so far leading to the clinical phenotype of Lynch syndrome (hereditary nonpolyposis colorectal cancer, HNPCC). Most mutations are private mutations. We report on nine novel pathogenic germline mutations that have been found in families meeting either the Amsterdam or the Bethesda criteria. These findings include the mutations MLH1,c.884+4A>G, MLH1,c.1377_1378insA;p.Glu460ArgfsX19, MLH1,c.1415_1416delGA;p.Arg472ThrfsX5, MSH2,c.301G>T;p.Glu101X, MSH2,c.638_639delTG;p.Leu213GlnfsX18, MSH2,c.842C>A;p.Ser281X, MSH2,c.859G>T;p.Gly287X, MSH6,c.2503C>T;p.Gln835X and a large genomic deletion of exons 1-10 of the PMS2 gene. The mutation MLH1,c.884+4A>G detected in two families results in a complete skipping of exon 10 on mRNA level and thus has been considered as pathogenic. In all cases the tumor tissue of the index patient revealed high microsatellite instability (MSI-H) and showed a complete loss of expression of the affected protein in the tumor cells by immunohistochemistry (IHC). The findings underline the importance of a pre-screening of tumor tissue for an efficient definition of conspicuous cases.

Aberrant splicing in MLH1 and MSH2 due to exonic and intronic variants.

Single base substitutions in DNA mismatch repair genes which are predicted to lead either to missense or silent mutations, or to intronic variants outside the highly conserved splicing region are often found in hereditary nonpolyposis colorectal cancer (HNPCC) families. In order to use the variants for predictive testing in persons at risk, their pathogenicity has to be evaluated. There is growing evidence that some substitutions have a detrimental influence on splicing. We examined 19 unclassified variants (UVs) detected in MSH2 or MLH1 genes in patients suspected of HNPCC for expression at RNA level. We demonstrate that 10 of the 19 UVs analyzed affect splicing. For example, the substitution MLH1,c.2103G > C in the last position of exon 18 does not result in a missense mutation as theoretically predicted (p.Gln701His), but leads to a complete loss of exon 18. The substitution MLH1,c.1038G > C (predicted effect p.Gln346His) leads to complete inactivation of the mutant allele by skipping of exons 10 and 11, and by activation of a cryptic intronic splice site. Similarly, the intronic variant MLH1,c.306+2dupT results in loss of exon 3 and a frameshift mutation due to a new splice donor site 5 bp upstream. Furthermore, we confirmed complete exon skipping for the mutations MLH1,c.1731G > A and MLH1,c.677G > A. Partial exon skipping was demonstrated for the mutations MSH2,c.1275A > G, MLH1,c.588+5G > A, MLH1,c.790+4A > G and MLH1,c.1984A > C. In contrast, five missense mutations (MSH2,c.4G > A, MSH2,c.2123T > A, MLH1,c.464T > G, MLH1,c.875T > C and MLH1,c.2210A > T) were found in similar proportions in the mRNA as in the genomic DNA. We conclude that the mRNA examination should precede functional tests at protein level.

Hereditary nonpolyposis colorectal cancer: pitfalls in deletion screening in MSH2 and MLH1 genes.

Hereditary nonpolyposis colorectal cancer (HNPCC) is caused by a deficiency in DNA mismatch repair in consequence of germline mutations mainly in the genes MSH2 and MLH1. Around 10% of patients suspected of HNPCC are identified with large genomic deletions that cannot be detected by conventional methods of mutation screening. The recently developed multiplex ligation-dependent probe amplification (MLPA) proved to be an easy to perform method for deletion detection and is reliable when more than one exon is deleted. We show that, in some cases, apparent deletions of single exons may actually result from single base substitutions or small insertions/deletions in the hybridisation sequence of MLPA probes. We conclude that single exon deletions, detected by MLPA or multiplex PCR, should be validated with additional methods.