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Reduced penetrance in familial Avellino corneal dystrophy associated with TGFBI mutations.

ABSTRACT: PURPOSE: To characterize the clinical phenotype, histopathological features, and molecular genetic basis of an Avellino corneal dystrophy (ACD) in a Chinese family. METHODS: A complete ophthalmologic examination was performed in 21 individuals (6 affected and 15 unaffected) of the four-generation family. DNA was obtained from peripheral blood leukocytes of each participant. Genetic analysis included TGFBI polymerase chain reaction (PCR) amplification and automated nucleotidic sequenceing of all 17 exons of genomic DNA. Histological analysis of corneal tissue from the proband was performed after a penetrating keratoplasty. One hundred Chinese controls were scanned for the presence of the R124H mutation by amplifying TGFBI exon 4 and then by direct sequencing of PCR products. RESULTS: The proband of the pedigree had phenotypic features consistent with diagnosis of ACD. He was homozygous for the same R124H mutation in TGFBI as previously reported in Japan and European countries. In addition, 4 affected and 7 unaffected individuals carried the same variation in the heterozygous state were identified. None of the 100 control subjects was positive for this mutation. Moreover, a variable expressivity and an apparent non-penetrance were observed in the individuals with heterozygous R124H mutation in our pedigree. After excluding the missed diagnosis or a late onset, it could be interpreted as a reduced penetrance. CONCLUSIONS: We reported a novel ACD family which exhibited a reduced penetrance of phenotype in northern China. This outcome supports that although the R124H mutation is one of the genetic causes of the disease, different genetic and environmental factors may influence the expressivity and the penetrance. Uncovering the mechanism may facilitate us to inhibit the occurrence of the corneal dystrophy caused by the R124H mutation in TGFBI, irrespective of the homozygous and heterozygous mutation.

SUBMITTER: Cao W

PROVIDER: S-EPMC2622714 | biostudies-literature | 2009

REPOSITORIES: biostudies-literature

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Reduced penetrance in familial Avellino corneal dystrophy associated with TGFBI mutations.

Cao Wenping W Ge Hongyan H Cui Xiaobo X Zhang Lu L Bai Jing J Fu Songbin S Liu Ping P

Molecular vision 20090114

<h4>Purpose</h4>To characterize the clinical phenotype, histopathological features, and molecular genetic basis of an Avellino corneal dystrophy (ACD) in a Chinese family.<h4>Methods</h4>A complete ophthalmologic examination was performed in 21 individuals (6 affected and 15 unaffected) of the four-generation family. DNA was obtained from peripheral blood leukocytes of each participant. Genetic analysis included TGFBI polymerase chain reaction (PCR) amplification and automated nucleotidic sequen ...[more]

PMID: 19145249

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Project description:PURPOSE: To report the clinical, ophthalmic, and genetic characteristics for lattice corneal dystrophy type I (LCDI) in a Chilean family. METHODS: Six affected family members were examined clinically including visual acuity, color cornea photography, applanation tonography, and fundoscopy. Genomic DNA was extracted from peripheral leukocytes from six affected and three unaffected members of a family with lattice corneal dystrophy type I. Exon 4 of the transforming growth factor-induced gene (TGFBI) was screened for the most frequent mutation, R124C, in the proband by sequencing. We also designed a rapid polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method to analyze the same mutation, amplifying exon 4 and digesting with PstI restriction enzyme. Using this strategy, we analyzed the mutation in six affected and three healthy family members. RESULTS: Three generations of family members were positively diagnosed with lattice corneal dystrophy. Six participants demonstrated LCD1 in both eyes, most of whom were symmetric. Age at onset of symptoms was variable (3-42 years old). Moreover, in this family, the age of onset of the disease decreased in succeeding generations, which could be interpreted as anticipation. Visual acuity varied from 1.0 to 0.13. Two patients, ages 69 and 44 years old, demonstrated a degree of severity "Bad" according to best-corrected vision and corneal commitment. The exon 4 sequence of TGFBI of the proband exhibits the heterozygous single-nucleotide mutation, C417T, leading to amino acid substitution (R124C) in the encoded TGF-induced protein. Using PCR-RFLP, we confirmed the heterozygous mutation in six affected family members and excluded it in three healthy members. CONCLUSIONS: The R124C mutation in TGFBI cosegregated with LCD type I in the investigated family. This is the first report of a molecular analysis of LCD type I in Chilean patients. The early onset affected persons in the fourth generation raises the possibility of anticipation.

Dataset Information

Reduced penetrance in familial Avellino corneal dystrophy associated with TGFBI mutations.

Publications

Reduced penetrance in familial Avellino corneal dystrophy associated with TGFBI mutations.

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