Molecular mechanism of congenital cataract induced by heat shock transcription factor 4 gene mutation in lop11 mouse

Abstract

Background Mutation of the heat shock transcription factor 4 （HSF4） gene causes autosomal recessive hereditary cataract in lens opacity locus 11 （lopl I ） mouse, but the molecular mechanism of the pathogenesis has not been determined. Objective This study was to investigate the molecular mechanism of congenital cataract induced by HSF4 gene mutation in lopll mouse. Methods Twenty-four lopll mice and 24 wild type C57BL/6 mice were used in this study. The animals were sacrificed and the lenses were obtained on postnatal days 1,7 and 12. Regular pathological examination was carried out to evaluate the morphological changes of the lens and count the number of lens epithelial ceils （LECs） in the mice. The ctB-Crystallin （CRYAB） content in the lenses was detected in postnatal day 1 mice by Western blot. The expression of the fibroblast growth factor （FGF） mRNA in the lenses was assayed by quantitative PCR （q-PCR）. The data were compared between the lopl 1 mice and wild type C57BL/6 mice with independent sample t test. The use and care of the experimental animals complied with the ARVO statement. Results The morphology and array of LECs were uniform and regular in the wild type C57BL/6 mice, while proliferation of LECs and disorder of lens fibers were seen in the lopll mice on postnatal day 1. On postnatal day 7,vacuolar degeneration of the lens appeared in 7-day-old lopll mice. The numbers of LECs were （417±19）, （467±16） and （489 ±21 ） in lopll mice on the postnatal day 1,7 and 12, respectively, and those of wild type C57BL/6 mice were （ 378 ± 13 ） , （ 391 ±9 ） and （ 395 ±7 ） , respectively, showing statistically significant differences between them （1 day：t=6.696,P=0. O00;7 days：t=6.578,P=0.000;14 days：t=7.240,P=0.000）. The expression of CRYAB in the lenses was evidently weaker in the 1-day-old lopll mice compared with wild type C57BL/6 mice. The relative folds of expression of FGF-1, FGF-4, FGF-7 mRNA in the lenses were significantly higher in the lopll mice than those in the wild type C57BL/6 mice （2.04±0. 13 vs. 1. 037±0.06;2.0±0.08 vs. 0.97± 0.08;4.59±0.12 vs.1.0±0.04） （FGF-1 mRNA：t=14.000,P〈0.001;FGF-4 mRNA：t=15.510,P〈0.01;FGF-7 mRNA：t = 29.41 ,P〈0.01 ）. Conclusions HSF4 mutation leads to the abnormal development of the lens in lopl 1 mice by arresting the expression of cLB-Crystallin protein and increasing the expression of the FGF gene. Key words: Gene mutation; Heat shock transcription factor; Cataract/congenital; Crystallin; Fibroblast growth factor