The genetic spectrum of achromatopsia in consanguineous families: insights from Whole exome sequencing across 15 affected individuals.

INTRODUCTION

Achromatopsia (ACHM) is a rare, inherited disorder in which patients cannot distinguish colors. The clinical phenotypes include light sensitivity, impaired color vision, partial or complete loss of photoreceptor function, reduced visual acuity and nystagmus. To date, six genes (CNGA3, CNGB3, GNAT2, PDE6H, PDE6C, and ATF6) are known to be the primary causes of ACHM, affecting the normal function of the cone photoreceptors.

METHODOLOGY: Whole-exome sequencing was performed in five families with 15 affected individuals. Candidate variants, prioritized using VARDIGS, were confirmed by Sanger sequencing and evaluated according to ACMG (2015) criteria. In-silico protein modeling and molecular dynamics simulations were employed to predict structural consequences of the variants.

RESULTS

All affected individuals exhibited hallmark clinical features of congenital achromatopsia, including vision loss, photophobia, night blindness, color blindness, refractive errors (myopia/hyperopia), and nystagmus. Notably, progressive vision loss was observed in three families. Four homozygous pathogenic variants were identified: CNGA3:c.1641C > A p.(Phe547Leu), CNGB3:c.199_200delAC p.(Thr67GlnfsTer20), CNGB3:c.1214T > C p.(Leu405Ser), and PDE6C: c.1336 G > T p.(Glu446Ter), all consistent with cone dystrophies phenotypes.

CONCLUSION

Our findings expand the mutational spectrum of achromatopsia and other inherited retinal diseases. To the best of our knowledge, these variants have been reported for the first time in Pakhtun ethnic group of Pakistani population. The identification of pathogenic variants provides valuable insight for future research on gene therapy eligibility and personalized medicine.