title: Two novel missense substitutions in the VSX1 gene: clinical and genetic analysis of families with Keratoconus from India.
abstract: BACKGROUND
  Visual system homeobox gene (VSX1) plays a major role in the early development of craniofacial and ocular tissues including cone opsin gene in the human retina. To date, few disease-causing mutations of VSX1 have been linked to familial and sporadic keratoconus (KC) in humans. In this study, we describe the clinical features and screening for VSX1 gene in families with KC from India.
  
  
  METHODS
  Clinical data and genomic DNA were collected from patients with clinically diagnosed KC and their family members. The study was conducted on 20 subjects of eight families from India. The coding exons of VSX1 gene were amplified using PCR and amplicons were analyzed by direct sequencing. Predictive effect of the mutations was performed using Polyphen-2, SIFT and mutation assessor algorithms. Additionally, haplotypes of VSX1 gene were constructed for affected and unaffected individuals using SNPs.
  
  
  RESULTS
  In the coding region of VSX1, one novel missense heterozygous change (p.Leu268His) was identified in five KC patients from two unrelated families. Another family of three members had a novel heterozygous change (p.Ser251Thr). These variants co-segregated with the disease phenotype in all affected individuals but not in the unaffected family members and 105 normal controls. In silico analysis suggested that p.Leu268His could have a deleterious effect on the protein coded by VSX1, while p.Ser251Thr has a neutral effect on the functional properties of VSX1. Haplotype examination revealed common SNPs around the missense change (p.Leu268His) in two unrelated KC families.
  
  
  CONCLUSIONS
  In this study, we add p.Leu268His, a novel missense variation in the coding region of VSX1 to the existing repertoire of VSX1 coding variations observed in Indian patients with the characteristic phenotype of KC. The variant p.Ser251Thr might be a benign polymorphism, but further biophysical studies are necessary to evaluate its molecular mechanism. The shared haplotype by two families with the same variant suggests the possibility of a founder effect, which requires further elucidation. We suggest that p.Leu268His might be involved in the pathogenesis of KC, which may help in the genetic counselling of patients and their family.
authors.affiliation: Cornea and Refractive Surgery Department, Narayana Nethralaya Postgraduate Institute of Ophthalmology, Bangalore, India. drrohitshetty@yahoo.com.
authors.forename: Rohit
authors.initials: R
authors.lastname: Shetty
authors.affiliation: Cornea Clinic, Department of Ophthalmology, Maastricht University Medical Center, 6211 LK, Maastricht, The Netherlands. rudy.nuijts@mumc.nl.
authors.forename: Rudy M M A
authors.initials: RM
authors.lastname: Nuijts
authors.affiliation: Cornea and Refractive Surgery Department, Narayana Nethralaya Postgraduate Institute of Ophthalmology, Bangalore, India. soumya.kaveri@gmail.com.
authors.forename: Soumya Ganesh
authors.initials: SG
authors.lastname: Nanaiah
authors.affiliation: GROW Research Laboratory, Narayana Nethralaya Foundation, Bangalore, India. ramanagene@gmail.com.
authors.forename: Venkata Ramana
authors.initials: VR
authors.lastname: Anandula
authors.affiliation: GROW Research Laboratory, Narayana Nethralaya Foundation, Bangalore, India. arkasubhra@narayananethralaya.com.
authors.forename: Arkasubhra
authors.initials: A
authors.lastname: Ghosh
authors.affiliation: Cornea and Refractive Surgery Department, Narayana Nethralaya Postgraduate Institute of Ophthalmology, Bangalore, India. drchaitra@hotmail.com.
authors.forename: Chaitra
authors.initials: C
authors.lastname: Jayadev
authors.affiliation: Cornea and Refractive Surgery Department, Narayana Nethralaya Postgraduate Institute of Ophthalmology, Bangalore, India. dr.natashapahuja@gmail.com.
authors.forename: Natasha
authors.initials: N
authors.lastname: Pahuja
authors.affiliation: GROW Research Laboratory, Narayana Nethralaya Foundation, Bangalore, India. gkumarmvel@gmail.com.
authors.forename: Govindasamy
authors.initials: G
authors.lastname: Kumaramanickavel
authors.affiliation: GROW Research Laboratory, Narayana Nethralaya Foundation, Bangalore, India. drnallathambi@narayananethralaya.com.
authors.forename: Jeyabalan
authors.initials: J
authors.lastname: Nallathambi
mesh_terms: D000293:Adolescent; D000328:Adult; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D019295:Computational Biology; D005136:Eye Proteins / Q000737:chemistry / Q000235:genetics*; D005260:Female; D006239:Haplotypes; D018398:Homeodomain Proteins / Q000737:chemistry / Q000235:genetics*; D006801:Humans; D007194:India; D007640:Keratoconus / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D010375:Pedigree; D055815:Young Adult
chemical_list: D005136:Eye Proteins; D018398:Homeodomain Proteins; C491583:VSX1 protein, human