Prof Yulin Chen

Abstract:

Background

Primary hypertrophic osteoarthropathy (PHO) is a genetically and clinically heterogeneous systematic disorder caused by mutations in genes HPGD and SLCO2A1. The purpose of the present study is to provide useful information for the early and precise diagnosis of PHO and identify causative mutations in Chinese PHO children.

Methods and results

The clinical manifestations, radiographic features of seven Chinese pediatric patients were systematically analyzed. Targeted exome sequencing identified a previously reported c.310_311delCT mutation and a novel common splicing site mutation c.324 + 5G > A in the HPGD gene. Relative quantitative real time PCR validated a novel deletion of the exon 4 in the same gene. Neither mutations nor structural variations in the gene SLCO2A1 were detected.

Conclusions

In the present study, homozygous or compound heterozygous HPGD mutations were identified in seven Chinese pediatric patients, suggesting an autosomal recessive inheritance. The c.310_311delCT mutation and the splicing site mutation c.324 + 5G > A were likely to be mutational hotspots in Chinese PHO patients. For the first time, a structural variation of the HPGD gene was reported. Homozygous, compound heterozygous mutations or structural variation identified in the HPGD gene proposed that targeted exome sequencing may be a preferable method for pediatric PHO diagnosis and mutation analysis.

Abstract:

Hereditary multiple osteochondroma (HMO) is one of the most common genetic skeletal disorders. It is caused by mutations in either EXT1 or EXT2 resulting in abnormal skeletal growth and morphogenesis. However, the spectrum and frequency of EXT1 and EXT2 mutations in Chinese patients with HMO was not previously investigated.Mutations were identified by performing Sanger sequencing analysis of the complete coding regions and flanking intronic sequences of EXT1 and EXT2, followed by multiplex ligation-dependent probe amplification (MLPA) analysis to detect gene deletions or duplications that could not be identified by the Sanger sequencing method.The present study identified pathogenic mutations in 93% (68/73) of unrelated HMO probands from 73 pedigrees. Mutations in EXT1 and EXT2 were identified in 53% (39/73) and 40% (29/73) of families. We identified 58 distinct mutations in EXT1 and EXT2, including 20 frameshift mutations, 16 nonsense mutations, 7 missense mutations, 9 splice site mutations, 5 large deletions, and 1 in-frame deletion mutation. Twenty-six of these mutations were novel and 32 were previously reported. Most of the mutations in EXT1 were base deletions or insertions (21/33), whereas the majority of those in EXT2 were single base substitution (18/25).Complete sequencing of both the EXT1 and EXT2 followed by MLPA analysis is recommended for genetic analysis of Chinese patients with HMO. This study provides a comprehensive characterization of the genetic aberrations found in Chinese patients with HMO and highlights the diagnostic value of molecular genetic analysis in this particular disease.