Two cases with de novo 3q26.31 microdeletion suggest a role for FNDC3B in human craniofacial development.

Here, we report strong evidence for a role of the FNDC3B gene in craniofacial development. Chromosomal microarray identified deletions at 3q26.31 in two patients with dysmorphic facial features. Parental FISH studies demonstrated that they are de novo; therefore, these two 3q26.31 microdeletions likely contribute to the patients' dysmorphic features. Interestingly, the minimal region of overlap contains only the FNDC3B gene. Ffibronectin domain III-containing protein 3B (FNDC3B), also known as factor for adipocyte differentiation-104 (FAD104), was first identified as a positive regulator of adipogenesis in a mouse model. Excitingly, further studies in a mouse model have recently demonstrated that FNDC3B is required for normal calvarial bone formation and negatively regulated calvarial cell differentiation through inhibition of BMP/Smad signaling. fndc3b-deficient mice have multiple cranial and skeletal malformations, such as craniosynostosis-like premature calvarial ossification, and skeletal deformities in the anterior fontanel and femurs. In summary, we report the first two patients with de novo 3q26.31 microdeletions. Both have dysmorphic features, consistent with the phenotypes seen in fndc3b-deficient mice in animal studies, which imply a critical role of FNDC3B in human craniofacial development. © 2016 Wiley Periodicals, Inc.

Congenital thrombocytopenia in a neonate with an interstitial microdeletion of 3q26.2q26.31.

Interstitial deletions encompassing the 3q26.2 region are rare. Only one case-report was published this far describing a patient with an interstitial deletion of 3q26.2 (involving the MDS1-EVI1 complex (MECOM)) and congenital thrombocytopenia. In this report we describe a case of a neonate with congenital thrombocytopenia and a constitutional 4.52 Mb deletion of 3q26.2q26.31 including TERC and the first 2 exons of MECOM, involving MDS1 but not EVI1. The deletion was demonstrated by array-CGH on lymphocytes. Our report confirms that congenital thrombocytopenia can be due to a constitutional deletion of 3q26.2 involving MECOM. We suggest that in case of unexplained neonatal thrombocytopenia, with even just slight facial dysmorphism, DNA microarray on peripheral blood should be considered early in the diagnostic work-up.