Role of FOXC2 and PITX2 rare variants associated with mild functional alterations as modifier factors in congenital glaucoma

PLoS One. 2019 Jan 18;14(1):e0211029. doi: 10.1371/journal.pone.0211029. eCollection 2019.

Abstract

Congenital glaucoma (CG) is a severe and inherited childhood optical neuropathy that leads to irreversible visual loss and blindness in children. CG pathogenesis remains largely unexplained in most patients. Herein we have extended our previous studies to evaluate the role of FOXC2 and PITX2 variants in CG. Variants of the proximal promoter and transcribed sequence of these two genes were analyzed by Sanger sequencing in a cohort of 133 CG families. To investigate possible oligogenic inheritance involving FOXC2 or PITX2 and CYP1B1, we also analyzed FOXC2 and PITX2 variants in a group of 25 CG cases who were known to carry CYP1B1 glaucoma-associated genotypes. The functional effect of three identified variants was assessed by transactivation luciferase reporter assays, protein stability and subcellular localization analyses. We found eight probands (6.0%) who carried four rare FOXC2 variants in the heterozygous state. In addition, we found an elevated frequency (8%) of heterozygous and rare PITX2 variants in the group of CG cases who were known to carry CYP1B1 glaucoma-associated genotypes, and one of these PITX2 variants arose de novo. To the best of our knowledge, two of the identified variants (FOXC2: c.1183C>A, p.(H395N); and PITX2: c.535C>A, p.(P179T)) have not been previously identified. Examination of the genotype-phenotype correlation in this group suggests that the presence of the infrequent PITX2 variants increase the severity of the phenotype. Transactivation reporter analyses showed partial functional alteration of three identified amino acid substitutions (FOXC2: p.(C498R) and p.(H395N); PITX2: p.(P179T)). In summary, the increased frequency in PCG patients of rare FOXC2 and PITX2 variants with mild functional alterations, suggests they play a role as putative modifier factors in this disease further supporting that CG is not a simple monogenic disease and provides novel insights into the complex pathological mechanisms that underlie CG.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Substitution
  • Cytochrome P-450 CYP1B1 / genetics
  • Cytochrome P-450 CYP1B1 / metabolism
  • Female
  • Forkhead Transcription Factors* / genetics
  • Forkhead Transcription Factors* / metabolism
  • Glaucoma* / congenital
  • Glaucoma* / metabolism
  • HEK293 Cells
  • Heterozygote
  • Homeodomain Proteins* / genetics
  • Homeodomain Proteins* / metabolism
  • Humans
  • Male
  • Multifactorial Inheritance*
  • Mutation, Missense*
  • Transcription Factors* / genetics
  • Transcription Factors* / metabolism

Substances

  • Forkhead Transcription Factors
  • Homeodomain Proteins
  • Transcription Factors
  • mesenchyme fork head 1 protein
  • homeobox protein PITX2
  • CYP1B1 protein, human
  • Cytochrome P-450 CYP1B1

Grant support

This study has been supported by research grants (to JE) from the “Instituto de Salud Carlos III/FEDER” (http://www.isciii.es, RD12/0034/0003, RD16/0008/0019, PI11/00662 and PI15/01193).