Three novel APC gene mutations in Portuguese FAP kindreds

Novel CHM mutations in Polish patients with choroideremia - an orphan disease with close perspective of treatment

Background

Choroideremia (CHM) is a rare X-linked recessive retinal dystrophy characterized by progressive chorioretinal degeneration in the males affected. The symptoms include night blindness in childhood, progressive peripheral vision loss and total blindness in the late stages. The disease is caused by mutations in the CHM gene encoding Rab Escort Protein 1 (REP-1). The aim of the study was to identify the molecular basis of choroideremia in five families of Polish origin.

Methods

Six male patients from five unrelated families of Polish ethnicity, who were clinically diagnosed with choroideremia, were examined in this study. An ophthalmologic examination performed in all the probands included: best-corrected visual acuity, slit-lamp examination, funduscopy, fluorescein angiography and perimetry. The entire coding region encompassing 15 exons and the flanking intronic sequences of the CHM gene were amplified with PCR and directly sequenced in all the patients.

Results

Five variants in the CHM gene were identified in the five families examined. Two of the variants were new: c.1175dupT and c.83C > G, while three had been previously reported.

Conclusions

This study provides the first molecular genetic characteristics of patients with choroideremia from the previously unexplored Polish population.

Profuse familial adenomatous polyposis with an adenomatous polyposis coli exon 3 mutation

The attenuated form of familial adenomatous polyposis coli (AAPC) is associated with mutations in the adenomatous polyposis coli (APC) gene which cluster in the 5' region of the gene. It has been proposed that a 'genotype-phenotype boundary' exists at codons 159-163, and mutations that are 5' of this boundary will produce AAPC. Herein we document a three-generation family with an exon 3 mutation well to the 5' side of the proposed boundary, in which two affected individuals have had, in their 40s, a profuse form of familial adenomatous polyposis coli. We conclude that the codon 159-163 'boundary' is indicative rather than definitive. These two patients also had postoperative intra-abdominal adhesions, severely so in one.

Visual impairment and REP-1 gene mutations in Japanese choroideremia patients

Choroideremia (CHM), an X-linked recessive hereditary disease, is an intractable chorioretinal dystrophy. The rate of disease progression of CHM reportedly shows considerable variability. A number of mutations involving the gene that codes for Rab escort protein-1 (REP-1) have been detected in CHM patients. We have analyzed REP-1 gene mutations of Japanese CHM patients. The present study was designed to investigate the clinical variability and the genotype to phenotype relationship in 15 Japanese CHM patients referred to the Department of Ophthalmology of Juntendo University Hospital. The clinical investigation of visual acuity, visual field, color vision and refraction revealed inter-individual variability. Mutation analyses of the REP-1 gene revealed 10 types of mutations in 13 patients from 11 families, including an insertion, small deletions, nonsense mutations and an A to CC mutation. In 13 CHM patients with detectable REP-1 gene mutations, no relationship of genotype to phenotype was detected. At present, we consider the REP-1 genotype to be an unreliable prognostic factor for counseling of CHM patients. In two patients from one family, no mutations were detected in coding regions of the REP-1 gene. These patients may have intron mutations of the REP-1 gene, not detectable by the techniques employed in this study, or other causative genes. Both were observed to have somewhat slower disease progression than the other 13 patients. More advanced analyses are necessary to answer questions regarding the genotype-phenotype relationship in CHM patients.