The Clinical Diagnosis And Molecular Genetic Analysis Of Osteopetrosis

Objective:To analyze the clinical manifestations and expression profiles of the 9 recruited families or only probands of suspected or clinically diagnosed osteopetrosis.To perform the genetic analysis in all the probands who suspected or clinically diagnosed ADOII by detecting the CLCN7 genes; and to perform the genetic analysis in all the probands who suspected or clinically diagnosed ARO with RTA by detecting the CAII genes. Then confirm the precise mutant sites and the type of each mutation.To predict the protein functions of all the missense mutations detected in this study, and try to explore their correlation between phenotype and genotype.Methods:9 recruited families/only probands of suspected or clinically diagnosed osteopetrosis in the Department of Endocrinology of Peking Union Medical College Hospital(PUMCH) since 2008.(1) We analyzed the inheritance patterns, clinical manifestations and radiographic features of the probands from 9 recruited families/only probands of suspected or clinically diagnosed osteopetrosis.(2) We amplified the CLCN7 gene and CAII gene of the 9 probands by using PCR techniques, then analyzed the direct nucleotide sequencing of all the PCRproducts, and confirmed the novel missense mutations in 50 unrelated healthy matched controls.(3) The protein functions of the all the missense mutations were predicted by Polyphen-2 software.(4) Characterization of the effect of splice-site mutation on CLCN7/CAII splicing by RT-PCR analysis.Results:1. We have identified seven novel mutations and two known mutations of CLCN7 in six Chinese families and two patients: a novel compound heterozygous mutation in one IARO patient. These findings enriched the database of CLCN7 mutations. We also summarized and compared the differences between ADO-II and IARO both in genotype and phenotype, which makes it available for clinicians to improve their understandings of osteopetrosis.2. We enriched the spectrum of mutations in CAII by identifying two novel mutations in two Chinese families with CAII deficiency syndrome. Careful clinical observation in combination with molecular genetic analysis would enrich the current understanding of CAII deficiency syndrome considerably. We supposed that truncation mutation and nonsense mutation can lead to shorter truncated products,which might be related to the severe clinical phenotypes in the patient. Future analysis of more cases is still needed to clarify the distribution and frequency of CAII gene mutations and the phenotype-genotype relationship in Chinese patients with CAII deficiency syndrome.