Arhinia, or absence of the nose, is a rare malformation of unknown etiology that is often accompanied by ocular and reproductive defects. Sequencing of 40 people with arhinia revealed that 84% of probands harbor a missense mutation localized to a constrained region of SMCHD1 encompassing the ATPase domain. SMCHD1 mutations cause facioscapulohumeral muscular dystrophy type 2 (FSHD2) via a trans-acting loss-of-function epigenetic mechanism. We discovered shared mutations and comparable DNA hypomethylation patterning between these distinct disorders. CRISPR/Cas9-mediated alteration of smchd1 in zebrafish yielded arhinia-relevant phenotypes. Transcriptome and protein analyses in arhinia probands and controls showed no differences in SMCHD1 mRNA or protein abundance but revealed regulatory changes in genes and pathways associated with craniofacial patterning. Mutations in SMCHD1 thus contribute to distinct phenotypic spectra, from craniofacial malformation and reproductive disorders to muscular dystrophy, which we speculate to be consistent with oligogenic mechanisms resulting in pleiotropic outcomes.

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S19 01The Queen Bee phenomenon in Canadian surgical subspecialties: an evaluation of gender biases in the resident training environment.

Following publication of this article, the authors were asked to remove a clinical image and some video footage of one of the affected individuals. Although consent was obtained, in keeping with their ethical consent framework, the authors allow for withdrawal of consent and are carrying out the wishes of the research subjects under their consent process. This amendment has been made in the HTML and PDF versions of the article.Corrigendum: SMCHD1 mutations associated with a rare muscular dystrophy can also cause isolated arhinia and Bosma arhinia microphthalmia syndrome In the version of this article initially published, the legend to Figure 4c stated that only one proband without SMCHD1 mutation was tested for D4Z4 methylation pattern. However, three probands and one affected family member without SMCHD1 mutation were tested, as shown in the figure. The error has been corrected in the HTML and PDF versions of the article.

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