Mutation spectrum of the FZD-4, TSPAN12 AND ZNF408 genes in Indian FEVR patients.
BACKGROUND
Mutations in candidate genes that encode for a ligand (NDP) and receptor complex (FZD4, LRP5 and TSPAN12) in the Norrin β-catenin signaling pathway are involved in the pathogenesis of familial exudative vitreoretinopathy (FEVR, MIM # 133780). Recently, a transcription factor (ZNF408) has also been implicated in FEVR. We had earlier characterized the variations in NDP among FEVR patients from India. The present study aimed at understanding the involvement of the remaining genes (FZD4, TSPAN12 and ZNF408) in the same cohort.


METHODS
The DNA of 110 unrelated FEVR patients and 115 unaffected controls were screened for variations in the entire coding and untranslated regions of these 3 genes by resequencing. Segregation of the disease-associated variants was assessed in the family members of the probands. The effect of the observed missense changes were further analyzed by SIFT and PolyPhen-2 scores.


RESULTS
The screening of FZD4, TSPAN12 and ZNF408 genes identified 11 different mutations in 15/110 FEVR probands. Of the 11 identified mutations, 6 mutations were novel. The detected missense mutations were mainly located in the domains which are functionally crucial for the formation of ligand-receptor complex and as they replaced evolutionarily highly conserved amino acids with a SIFT score < 0.005, they are predicted to be pathogenic. Additionally 2 novel and 16 reported single nucleotide polymorphisms (SNP) were also detected.


CONCLUSIONS
Our genetic screening revealed varying mutation frequencies in the FZD4 (8.0 %), TSPAN12 (5.4 %) and ZNF408 (2.7 %) genes among the FEVR patients, indicating their potential role in the disease pathogenesis. The observed mutations segregated with the disease phenotype and exhibited variable expressivity. The mutations in FZD4 and TSPAN12 were involved in autosomal dominant and autosomal recessive families and further validates the involvement of these gene in FEVR development.
Kallam Anji Reddy Molecular Genetics Laboratory, Brien Holden Eye Research Centre, L V Prasad Eye Institute (KAR Campus), Road#2, Banjara Hills, Hyderabad, 500034, India.
Ganeswara Rao
GR
Musada
Kallam Anji Reddy Molecular Genetics Laboratory, Brien Holden Eye Research Centre, L V Prasad Eye Institute (KAR Campus), Road#2, Banjara Hills, Hyderabad, 500034, India.
Hameed
H
Syed
Smt. Kanuri Santhamma Centre for Vitreo Retinal Diseases, LV Prasad Eye Institute, Hyderabad, India.
Subhadra
S
Jalali
Kallam Anji Reddy Molecular Genetics Laboratory, Brien Holden Eye Research Centre, L V Prasad Eye Institute (KAR Campus), Road#2, Banjara Hills, Hyderabad, 500034, India.
Subhabrata
S
Chakrabarti
Kallam Anji Reddy Molecular Genetics Laboratory, Brien Holden Eye Research Centre, L V Prasad Eye Institute (KAR Campus), Road#2, Banjara Hills, Hyderabad, 500034, India. inderjeet@lvpei.org.
Inderjeet
I
Kaur
D000368:Aged; D044466:Asian People / Q000235:genetics*; D016022:Case-Control Studies; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000235:genetics*; D005260:Female; D051157:Frizzled Receptors / Q000235:genetics*; D005787:Gene Frequency; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation; D016133:Polymerase Chain Reaction / Q000379:methods; D012164:Retinal Diseases / Q000235:genetics*; D059470:Tetraspanins / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics*
D004268:DNA-Binding Proteins; C402930:FZD4 protein, human; D051157:Frizzled Receptors; C545100:TSPAN12 protein, human; D059470:Tetraspanins; D014157:Transcription Factors; C582974:ZNF408 protein, human
Abnormal angiogenesis; Candidate genes; Mutation screening; Retina