Mycndeficiency underlies the development of orofacial clefts in mice and humans

Abstract

Non-syndromic cleft lip with or without cleft palate (NSCL/P) is the most common subphenotype of non-syndromic orofacial clefts (NSOFCs) arising from genetic and/or environmental perturbations during embryonic development. We previously identified 2p24.2 as a risk locus associated with NSCL/P in the Chinese Han population, and MYCN is a candidate risk gene in this region. To understand the potential function of MYCN in craniofacial development, we generated Wnt1-Cre;Mycnflox/flox mice that exhibited cleft palate, microglossia, and micrognathia, resembling the Pierre Robin sequence (PRS) in humans. Further analyses indicated that the cleft palate was secondary to the delayed elevation of palatal shelves caused by micrognathia. The micrognathia resulted from impaired chondrogenic differentiation in Merkel’s cartilage, which limited tongue development, leading to microglossia. In terms of mechanism, Mycn deficiency in cranial neural crest cells (CNCCs) downregulated Sox9 expression by inhibiting Wnt5a in a CNCC-derived chondrogenic lineage in Merkel’s cartilage. To investigate whether MYCN deficiency contributed to NSCL/P, we performed direct sequencing targeting all exons and exon-intron boundaries of MYCN in 104 multiplex families with mendelian NSCL/P and identified a novel pathogenic variant in MYCN. Taken together, our data indicate that ablation of Mycn in mouse CNCCs could resemble PRS by suppressing the Wnt5a-Sox9 signaling pathway in Merkel’s cartilage and that mutations in MYCN may be novel potential causes of NSCL/P.

Probabilistic inference of epigenetic age acceleration from cellular dynamics

“…This link was reinforced by the association of this locus with various cleft lip/palate traits (Extended Data Fig. 3e), for which MYCN deficiency is a known risk factor 26 . 27…”

Decreased Tiam1‐mediated Rac1 activation is responsible for impaired directional persistence of chondrocyte migration in microtia

“…Cranial neural crest cells (NCCs) are a migratory cell population and give rise to the majority of cartilage, 4 bone, 5 connective tissue and sensory ganglia 6 during craniofacial development. According to the most commonly reproduced version, auricle tissue is derived from NCCs that migrate into the first and second branchial arches.…”

Mechanical dissection and culture of mouse cranial neural crest cells

“…In previous studies, mice lacking Brca1 gene in the neural crests showed craniofacial abnormalities such as defective nasal‐frontal bones and smaller maxillary and mandibular bones (Kitami, Kitami, Kaku, Wang, & Komatsu, 2018). Knocking out Mycn in CNCCs could lead to the failure in palatal shelves elevation (Yang et al, 2022). Interference of SF3B2 resulted in disrupted formation of cranial neural crest precursor and subsequent craniofacial cartilage defects in Xenopus (Timberlake et al, 2021).…”