Abstract：
BACKGROUND: Syngnathia is an ultrarare craniofacial malformation characterised by an inability to open the mouth due to congenital fusion of the upper and lower jaws. The genetic causes of isolated bony syngnathia are unknown.
METHODS: We used whole exome and Sanger sequencing and microsatellite analysis in six patients (from four families) presenting with syngnathia. We used CRISPR/Cas9 genome editing to generate vgll2a and vgll4l germline mutant zebrafish, and performed craniofacial cartilage analysis in homozygous mutants.
RESULTS: We identified homozygous truncating variants in vestigial-like family member 2 (VGLL2) in all six patients. Two alleles were identified: one in families of Turkish origin and the other in families of Moroccan origin, suggesting a founder effect for each. A shared haplotype was confirmed for the Turkish patients. The VGLL family of genes encode cofactors of TEAD transcriptional regulators. Vgll2 is regionally expressed in the pharyngeal arches of model vertebrate embryos, and morpholino-based knockdown of vgll2a in zebrafish has been reported to cause defects in development of pharyngeal arch cartilages. However, we did not observe craniofacial anomalies in vgll2a or vgll4l homozygous mutant zebrafish nor in fish with double knockout of vgll2a and vgll4l. In Vgll2 -/- mice, which are known to present a skeletal muscle phenotype, we did not identify defects of the craniofacial skeleton.
CONCLUSIONS: Our results suggest that although loss of VGLL2 leads to a striking jaw phenotype in humans, other vertebrates may have the capacity to compensate for its absence during craniofacial development.
METHODS: We used whole exome and Sanger sequencing and microsatellite analysis in six patients (from four families) presenting with syngnathia. We used CRISPR/Cas9 genome editing to generate vgll2a and vgll4l germline mutant zebrafish, and performed craniofacial cartilage analysis in homozygous mutants.
RESULTS: We identified homozygous truncating variants in vestigial-like family member 2 (VGLL2) in all six patients. Two alleles were identified: one in families of Turkish origin and the other in families of Moroccan origin, suggesting a founder effect for each. A shared haplotype was confirmed for the Turkish patients. The VGLL family of genes encode cofactors of TEAD transcriptional regulators. Vgll2 is regionally expressed in the pharyngeal arches of model vertebrate embryos, and morpholino-based knockdown of vgll2a in zebrafish has been reported to cause defects in development of pharyngeal arch cartilages. However, we did not observe craniofacial anomalies in vgll2a or vgll4l homozygous mutant zebrafish nor in fish with double knockout of vgll2a and vgll4l. In Vgll2 -/- mice, which are known to present a skeletal muscle phenotype, we did not identify defects of the craniofacial skeleton.
CONCLUSIONS: Our results suggest that although loss of VGLL2 leads to a striking jaw phenotype in humans, other vertebrates may have the capacity to compensate for its absence during craniofacial development.
摘要：
背景：同颌畸形是一种颅面畸形，其特征是由于先天性上下颌融合而无法张口。孤立的骨性同颌病的遗传原因尚不清楚。
方法：我们对6例（来自4个家庭）表现为同颌畸形的患者进行了全外显子组和Sanger测序和微卫星分析。我们使用CRISPR/Cas9基因组编辑生成vgll2a和vgll4l种系突变斑马鱼，并对纯合突变体进行颅面软骨分析。
结果：我们在所有6名患者中鉴定出了存留样家族成员2（VGLL2）中的纯合截短变体。确定了两个等位基因：一个在土耳其血统的家庭中，另一个在摩洛哥血统的家庭中，为每个人暗示一个创始人的效果。为土耳其患者确认了共享的单倍型。VGLL基因家族编码TEAD转录调节因子的辅因子。Vgll2在模型脊椎动物胚胎的咽弓中区域表达，据报道，斑马鱼中基于吗啉代的vgll2a敲低会导致咽弓软骨发育缺陷。然而,我们没有观察到vgll2a或vgll4l纯合突变斑马鱼的颅面异常，也没有观察到vgll2a和vgll4l双敲除的鱼的颅面异常。在Vgll2-/-小鼠中，已知呈现骨骼肌表型，我们没有发现颅面骨骼的缺陷。
结论：我们的结果表明，尽管VGLL2的缺失导致人类下颌表型显著，其他脊椎动物可能有能力补偿颅面发育过程中的缺失。
方法：我们对6例（来自4个家庭）表现为同颌畸形的患者进行了全外显子组和Sanger测序和微卫星分析。我们使用CRISPR/Cas9基因组编辑生成vgll2a和vgll4l种系突变斑马鱼，并对纯合突变体进行颅面软骨分析。
结果：我们在所有6名患者中鉴定出了存留样家族成员2（VGLL2）中的纯合截短变体。确定了两个等位基因：一个在土耳其血统的家庭中，另一个在摩洛哥血统的家庭中，为每个人暗示一个创始人的效果。为土耳其患者确认了共享的单倍型。VGLL基因家族编码TEAD转录调节因子的辅因子。Vgll2在模型脊椎动物胚胎的咽弓中区域表达，据报道，斑马鱼中基于吗啉代的vgll2a敲低会导致咽弓软骨发育缺陷。然而,我们没有观察到vgll2a或vgll4l纯合突变斑马鱼的颅面异常，也没有观察到vgll2a和vgll4l双敲除的鱼的颅面异常。在Vgll2-/-小鼠中，已知呈现骨骼肌表型，我们没有发现颅面骨骼的缺陷。
结论：我们的结果表明，尽管VGLL2的缺失导致人类下颌表型显著，其他脊椎动物可能有能力补偿颅面发育过程中的缺失。
