Exome sequencing reveals a novel PTHLH mutation in a Chinese pedigree with brachydactyly type E and short stature

Brachydactyly includes shortening of digits due to abnormal development of phalanges, metacarpals, or both. It can occur either as an isolated malformation or with other anomalies as part of many congenital syndromes. It is included as one of the dysostosis groups affecting the limbs in the nosology and classification of genetic skeletal disorders. However, brachydactyly usually shows a high degree of phenotypic variability. In this study, we successfully identified a novel heterozygous mutation of the parathyroid hormone-like hormone (PTHLH) gene by exome sequencing in a Chinese pedigree with brachydactyly and short stature. The PTHLH gene encodes a parathyroid hormone-related protein (PTHrP) that is involved in the regulation of endochondral bone development, and mutations in this gene cause the type E form of brachydactyly. The mutation p.L15R occurs at a hydrophobic core region of the signal peptide, suggesting that this variation probably changes the signal peptide cleavage site at the in silico prediction. Further in vitro functional analysis showed that this mutation can lead to the retention of an N-terminal signal peptide fragment after the nascent proteins are translated.