| This thesis includes two parts: one is about the molecular genetic analyse of a family with dominant retinitis pigmentosa (RP), the other is analyse of heat shock transcription factor 4(HSF4)in a family with autosomal dominant congenital cataract(ADCC).Retinitis pigmentosa (RP) is a retinal degenerative disease characterized by constriction of the visual fields, night blindness, and fundus changes including bone spicule like pigmentation and a loss of photoreceptors. The X-linked retinitis pigmentosa (XLRP) is considered clinically the most severe form. In the present study, we investigated a Chinese family with dominant RP and additional cone dystrophy phenotypes. By linkage analysis we excluded the possibility of all known autosomal dominant RP (adRP) loci being the pathogenic gene of this RP family. Using microsatellite markers on X chromosome, we carried out further linkage and haplotype analysis and defined the disease interval between DXS1226 and DXS1068, where the RPGR gene is located. Direct DNA sequence analysis revealed a novel g.ORF15+1166delA mutation in ORF15 of RPGR in all affected hemizygous males and heterozygous female patients, but not in unaffected members of this family and 101 normal controls. The deletion results in a frameshift leading to long stretches of abnormal amino acid sequence and premature termination of translation of RPGR. These results suggest that the g.ORF15+1166delA was responsible for the disease in this family.In the previous identified X-Linked dominant RP families, the female carriers showed wide spectrum phenotypes, onset of the disease was delayed and symptoms were sometimes milder in females than hemizygous males, so it was considered as partial X-linked dominant RP. However, the affected females in the present study show no signs of delayed onset, and they are as severely affected as male patients in the family, so it is considered as complete X-linked dominant RP. The clinical features of the patients showed high intrafamilial variability, some affected individuals even showed cone dystrophy phnotypes, the g.ORF15+1166delA in the present study revealed the broader phenotypic spectrum of RPGR mutations. HSF4 belongs to the family of heat shock transcription factors. The mutations of HSF4 can cause ADCC. we clinically characterized a ADCC family, in order to test whether HSF4 mutation was responsible for the disease in this family, we PCR-amplified and directly DNA sequenced the whole coding sequence and exon-intron boundaries of HSF4. one C to T transversion at 331th nucleotide(c.C331T)of HSF4 was identified, the c.C331T transversion results in a substitution from arginine to cysteine at 111th codon of HSF4 (p.Arg111Cys). Subsequent restriction fragment length polymorphism (RFLP) analysis revealed that the p.Arg111Cys substitution does not co-segregate with the disease in the ADCC family. These results suggest that the c.C331T substitution was not the cause of congenital cataract in this family, but a common single nucleotide polymorphism (SNP). Our study shows that the amino acid substitution located in the important DNA-binding domain (DBD) of HSF4 was not always associated with congenital cataract. |
