SUMMARYMitral valve prolapse (MVP) is a common cardiac valve disease that affects nearly 1 in 40 individuals1–3. It can manifest as mitral regurgitation and is the leading indication for mitral valve surgery4,5. Despite a clear heritable component, the genetic etiology leading to non-syndromic MVP has remained elusive. Four affected individuals from a large multigenerational family segregating non-syndromic MVP underwent capture sequencing of the linked interval on chromosome 11. We report a missense mutation in the DCHS1 gene, the human homologue of the Drosophila cell polarity gene dachsous (ds) that segregates with MVP in the family. Morpholino knockdown of the zebrafish homolog dachsous1b resulted in a cardiac atrioventricular canal defect that could be rescued by wild-type human DCHS1, but not by DCHS1 mRNA with the familial mutation. Further genetic studies identified two additional families in which a second deleterious DCHS1 mutation segregates with MVP. Both DCHS1 mutations reduce protein stability as demonstrated in zebrafish, cultured cells, and, notably, in mitral valve interstitial cells (MVICs) obtained during mitral valve repair surgery of a proband. Dchs1+/− mice had prolapse of thickened mitral leaflets, which could be traced back to developmental errors in valve morphogenesis. DCHS1 deficiency in MVP patient MVICs as well as in Dchs1+/− mouse MVICs result in altered migration and cellular patterning, supporting these processes as etiological underpinnings for the disease. Understanding the role of DCHS1 in mitral valve development and MVP pathogenesis holds potential for therapeutic insights for this very common disease.

What is teaching and learning mathematics for social justice (TLMSJ)? How has TLMSJ been taken up in mathematics education—both historically and contemporarily? Along with unpacking these two central questions, another purpose of this article is to assess the current capacity and stance of TLMSJ toward addressing issues of racial injustice. We begin with an overview of TLMSJ as an epistemic perspective and introduce an analytical lens based on selected tenets of critical race theory. We then use this analytical lens to examine extant TLMSJ scholarship toward broadening the possibilities of justice-oriented scholarship in mathematics education.

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