Uncovering the profile of mutations of transforming growth factor beta-induced gene in Chinese corneal dystrophy patients

Mutation analysis of the TGFBI gene in pedigrees of lattice corneal dystrophy in Eastern China

BACKGROUND

To delineate the mutations of the TGFBI gene in Eastern China by whole-exome sequencing (WES) in eight Chinese families with lattice corneal dystrophy (LCD).

MATERIALS AND METHODS

This retrospective study included eight families with LCD from Eastern China. Clinical features were examined using slit-lamp examination, anterior segment optical coherence tomography, and in vivo confocal microscopy. Peripheral blood samples of probands were collected for WES, and saliva samples from family members were collected for TGFBI screening using Sanger sequencing. The physicochemical effects of mutations were investigated using bioinformatics tools.

RESULTS

Family 1 presented a classic LCD I with a p.R124C mutation of the TGFBI gene, while the other seven families were diagnosed with LCD IIIA. Six of the seven LCD IIIA families had heterozygous single-gene mutations (p.A546D, p.L565 H, p.T621P), and one had a compound heterozygous (cis) mutation (p.P501T and p.N622 H). The mutation of p.L565 H was the first time of integrated family report in contrast to the cases reported in 2019, and the p.T621P mutation was first reported in a Chinese population. Notably, the family with the compound mutation was associated with an obvious early-onset (in the 2nd decade of life) compared to the LCD IIIA patients with each single mutation (p.P501T or p.N622 H) showing late-onset (in the 7th decade of life).

CONCLUSIONS

WES is efficient for the genomic testing of LCD and genetic relationship identification in different families with the same mutated gene. We identified a compound heterozygous mutation (p.P501T and p.N622 H) and two mutations (p.T621P and p.L565 H) uncommon in China.

Deterioration of Avellino corneal dystrophy in a Chinese family after LASIK

AIM

To reveal the importance of TGFBI gene screening for candidates with a family history of corneal disease or granular opacities in corneal stroma before refractive surgery.

METHODS

A 37-year-old male (proband) underwent bilateral laser-assisted in situ keratomileusis (LASIK) in 2002, with right vision decreased significantly in 2006. The proband and other 32 members of the family underwent a detailed ophthalmic examination, including vision acuity, intraocular pressure, slit-lamp photograph, fundus examination, optical coherence tomography (OCT) of cornea, and in vivo confocal microscope (IVCM) and peripheral blood was used for genomic DNA extraction. Seventeen TGFBI gene exons were analyzed via polymerase chain reaction amplification and direct sequencing.

RESULTS

Slit-lamp, IVCM, and OCT images showed that a large amount of dense and confluent granular opaque were seen at the interfaces of the flap and remnant stromal bed in right and light degree in left eye. Sanger sequencing showed that there was a 371G>A mutation (CGC>CAC) in exon 4, which indicated that he harbored a heterozygote R124H mutation, identifying the diagnosis of Avellino corneal dystrophy (ACD). Among the other 32 family members, 6 of them harbored the identical mutation to that in the proband.

CONCLUSION

ACD will worsen and recur after LASIK. Preoperative gene-screening for TGFBI mutations is important in diagnosing ACD.

Novel mutation in the TGFBI gene in a Moroccan family with atypical corneal dystrophy: a case report

BACKGROUND

Corneal dystrophies (CDs) are a heterogeneous group of bilateral, genetically determined, noninflammatory bilateral corneal diseases that are usually limited to the cornea. CD is characterized by a large variability in the age of onset, evolution and visual impact and the accumulation of insoluble deposits at different depths in the cornea. Clinical symptoms revealed bilateral multiple superficial, epithelial, and stromal anterior granular opacities in different stages of severity among three patients of this family. A total of 99 genes are involved in CDs. The aim of this study was to identify pathogenic variants causing atypical corneal dystrophy in a large Moroccan family and to describe the clinical phenotype with severely different stages of evolution.

CASE PRESENTATION

In this study, we report a large Moroccan family with CD. Whole-exome sequencing (WES) was performed in the three affected members who shared a phenotype of corneal dystrophy in different stages of severity. Variant validation and familial segregation were performed by Sanger sequencing in affected sisters and mothers and in two unaffected brothers. Whole-exome sequencing showed a novel heterozygous mutation (c.1772C > A; p.Ser591Tyr) in the TGFBI gene. Clinical examinations demonstrated bilaterally multiple superficial, epithelial and stromal anterior granular opacities in different stages of severity among three patients in this family.

CONCLUSIONS

This report describes a novel mutation in the TGFBI gene found in three family members affected by different phenotypic aspects. This mutation is associated with Thiel-Behnke corneal dystrophy; therefore, it could be considered a novel phenotype genotype correlation, which will help in genetic counselling for this family.

Identification of a Heterozygous Mutation in the TGFBI Gene in a Hui-Chinese Family with Corneal Dystrophy

Background/Aims

Corneal dystrophies (CDs) belong to a group of hereditary heterogeneous corneal diseases which result in visual impairment due to the progressive accumulation of deposits in different corneal layers. So far, mutations in several genes have been responsible for various CDs. The purpose of this study is to identify gene mutations in a three-generation Hui-Chinese family associated with granular corneal dystrophy type I (GCD1).

Methods

A three-generation Hui-Chinese pedigree with GCD1 was recruited for this study. Slit-lamp biomicroscopy, optical coherence tomography, and confocal microscopy were performed to determine the clinical features of available members. Whole exome sequencing was performed on two patients to screen for potential disease-causing variants in the family. Sanger sequencing was used to test the variant in the family members.

Results

Clinical examinations demonstrated bilaterally abundant multiple grayish-white opacities in the basal epithelial and superficial stroma layers of corneas of the two patients. Whole exome sequencing revealed that a heterozygous missense mutation (c.1663C > T, p.Arg555Trp) in the transforming growth factor beta-induced gene (TGFBI) was shared by the two patients, and it cosegregated with this disease in the family confirmed by Sanger sequencing.

Conclusions

The results suggested that the heterozygous TGFBI c.1663C > T (p.Arg555Trp) mutation was responsible for GCD1 in the Hui-Chinese family, which should be of great help in genetic counseling for this family.

Analysis of TGFBI Gene Mutations in Three Chinese Families with Corneal Dystrophy

Objective

To identify the types of TGFBI (transforming growth factor, beta-induced) gene mutations in three Chinese families with Reis-Bücklers corneal dystrophy (RBCD), lattice corneal dystrophy type I (LCDI), or Avellino corneal dystrophy (ACD) and to investigate the relationship between the phenotypes and genotypes of corneal dystrophy.

Methods

Peripheral blood was collected from 24 patients and 76 phenotypically normal members in three Chinese families as well as from 100 healthy controls. Genomic DNA was extracted. All 17 exons of the TGFBI gene, and the exon-intron junctions were examined by polymerase chain reaction (PCR) and direct DNA sequencing to identify and analyse gene mutations. In addition, all members of the three families were subjected to detailed clinical examinations.

Results

The heterozygous c.371G > T (p.R124L) mutation was detected in exon 4 of the TGFBI gene in nine patients from the family with RBCD. In contrast, this mutation was not found in the phenotypically normal members of the family. The heterozygous c.370C > T (p.R124C) mutation was found in exon 4 of the TGFBI gene in 11 patients from the family with LCDI. This mutation was not found in the phenotypically normal members of the family. The heterozygous c.371G > A (p.R124H) mutation was detected in exon 4 of the TGFBI gene in four patients from the family with ACD. Again, this mutation was not found in the phenotypically normal members of the family. The TGFBI gene mutations cosegregated with the disease phenotypes in the three families and exhibited an autosomal dominant mode of inheritance. No TGFBI gene mutations were detected in the 100 healthy controls.

Conclusion

There is a high degree of correlation between the phenotypes and genotypes of TGFBI-linked corneal dystrophies. R124 represents a mutational hotspot in the TGFBI gene. Gene mutation analysis provides a reliable basis for the definitive diagnosis of corneal dystrophy.

Two mutations in the transforming growth factor beta-induced gene associated with familial Lattice corneal dystrophy

AIM

To report a phenotypic variant pedigree of lattice corneal dystrophy (LCD) associated with two mutations, R124C and A546D, in the transforming growth factor beta-induced gene (TGFBI).

METHODS

A detailed ocular examination was taken for all participants of a LCD family. Peripheral blood leukocytes from each participant were extracted to obtain the DNA. Polymerase chain reaction (PCR) of all seventeen exons of TGFBI gene was performed. The products were sequenced and analyzed. Histological examination was carried out after a penetrating keratoplasty from the right eye of proband.

RESULTS

Genetic analysis showed that the proband and all 6 affected individuals harbored both a heterozygous CGC to TGC mutation at codon 124 and a heterozygous GCC to GAC mutation at codon 546 of TGFBI. None of the 100 control subjects and unaffected family members was positive for these two mutations. Ocular examination displayed multiple refractile lattice-like opacities in anterior stroma of the central cornea and small granular deposits in the peripheral cornea. The deposits were stained positively with Congo red indicating be amyloid in nature and situated mainly in the anterior and middle stroma.

CONCLUSION

We observed a novel LCD family which carried two pathogenic mutations (R124C and A546D) in the TGFBI gene. The phenotypic features were apparently different from those associated with corresponding single mutations. The result reveals that although the definite mutation is the most important genetic cause of the disease, some different modifier alleles may influence the phenotype.