Genetical and Morphological Studies on Congenital Cataract and Microphthalmia (Cts) in Mice

Abstract

The autosomal semi-dominant gene Cts has been considered to manifest a congenital cataract in both heterozygous and homozygous conditions, and microphthalmia only in the homozygous one. The present study was undertaken to confirm the manifestations of microphthalmia even in the heterozygous state of Cts gene and to study the morphological change of the lenses in correlation with the microphthalmia. Measurements of the horizontal diameter of the cornea and weight of the eyeball proved that the eyeballs of heterozygotes were larger than those of homozygotes and smaller than those of unaffected animals. The results of various crosses among three different genotypic mice conformed to those expected for a single autosomal semi-dominant gene. Embryos and fetuses of each genotype at serial stages from day 9 to 20 of pregnancy were examined histologically. Then, swellin of the lens fiber cells was first detected in the homozygotes on day 14 of pregnancy. This change was followed by pyknosis of lens fiber cells and degeneration of fibers. Such changes arose in the later prenatal period and were less extensive in the heterozygous lenses. No faulty closure of embryonic fissure was found histologically in either homozygous or heterozygous eyes. Accordingly, the microphthalmia manifested by Cts gene was considered to be a consequence of developmental disturbance of the cataractous lens.