Microcephaly
Gene: WDR11
Haag et al (2021 - PMID: 34413497) report on 6 individuals from 3 unrelated families, harboring biallelic LoF WDR11 variants.
Common features included microcephaly (6/6 - range: -2.43 SD to -4.93SD) and intellectual disability (6/6, in 5 cases mild, in 1 severe) with some individuals presenting also with mild short stature.
Homozygosity or compound heterozygosity for LoF variants in affected individuals was identified following exome sequencing (fam1: NM_018117.12:c.1255C>T/p.Q419* hmz, fam2:c.3033_3036del/D1011Efs*21 in trans with c.1439del/p.N480Tfs*32, fam3:c.2931+1G>A hmz).
Segregation studies supported carrier state of parents and unaffected sibs (or homozygosity for wt allele in the latter).
Variable previous investigations incl. standard karyotype and CMA were normal in several subjects (notably index cases from each family).
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As the authors comment WDR11 encodes for the WD repeat domain 11 protein and has broad expression in the developing mouse CNS. Mutations in other genes encoding for WD repeat proteins have been associated with neurological, endocrine or other disorders incl. ciliopathies.
Heterozygous missense WDR11 variants are associated with hypogonadotropic hypogonadism (HH) 14 with or without anosmia (MIM #614858). [Gene2Phenotype : monoallelic, all missense/in-frame].
The authors performed extensive hormonal studies and argue that the phenotype associated with biallelic variants differs significantly from the dominantly inherited variants (HH) suggesting that biallelic variants result in a clinically distinct entity. In addition, carrier parents of the individuals reported by Haag et al had no obvious signs of congenital HH. However, there was no endocrinological examination performed.
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Variant effect:
Immunofluorescence studies demonstrated strong juxtanuclear WDR11 staining in control fibroblasts , but only cell-ubiquitous background labeling in patient fibroblasts (for Q419*). There was also evidence for colocalization of wt WDR11 to the trans-Golgi network (TGN) with loss of this pattern in patient fibroblasts (Q419*).
Western blot in whole cell lysates of cultured patient fibroblasts (same variant) proved loss of WDR11 irrespectively of the antibody used (against N- or C-terminal epitopes of WDR11). There was no indication of a truncated protein.
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Animal models:
The authors discuss previous evidence from mice/zebrafish models suggesting abnormal Hedgehog signaling in the primary cilium and impaired ciliogenesis due to loss of WDR11.
Wdr11-null mice display features of holoprosencephaly incl. microcephaly, hypotelorism, micro/anophthalmia, abnormal pituitary gland, growth retardation, heart defects, hypoplasia of reproductive organs and infertility. There was evidence of reduced length of the ciliary axoneme and reduced frequency of ciliated cells.
Knockdown of wdr11 in zebrafish led to microcephaly, aberrant head cartilage formation, microphthalmia, curved body axis, motility defects.
Overall the authors consider that the phenotype of microcephaly, variable growth delay and/or some visual/skeletal anomalies are recapitulated to some degree in animal models, although a more severe phenotype is observed in mice.
In the cohort presented by Haag et al there was no evidence of congenital heart defects, brain malformations, abnormal sexual hormone profiles or pituitary (MRI) abnormalities based on the investigations performed.
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The authors discuss briefly on the previously proposed role for WDR11 in endosome to trans Golgi network vesicular trafficking which might also be supported by their colocalization experiments in patient fibroblasts.
Sources: LiteratureCreated: 23 Aug 2021, 2:16 a.m.
Mode of inheritance
BIALLELIC, autosomal or pseudoautosomal
Phenotypes
Intellectual developmental disorder, autosomal recessive 78, MIM# 620237; Intellectual disability; Microcephaly; Short stature
Publications
Phenotypes for gene: WDR11 were changed from Intellectual disability; Microcephaly; Short stature to Intellectual developmental disorder, autosomal recessive 78, MIM# 620237; Intellectual disability; Microcephaly; Short stature
Gene: wdr11 has been classified as Green List (High Evidence).
Gene: wdr11 has been classified as Green List (High Evidence).
gene: WDR11 was added gene: WDR11 was added to Microcephaly. Sources: Literature Mode of inheritance for gene: WDR11 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: WDR11 were set to 34413497 Phenotypes for gene: WDR11 were set to Intellectual disability; Microcephaly; Short stature Review for gene: WDR11 was set to GREEN