Removal of Hsf4 leads to cataract development in mice through down-regulation of gamma S-crystallin and Bfsp expression.
BACKGROUND
Heat-shock transcription factor 4 (HSF4) mutations are associated with autosomal dominant lamellar cataract and Marner cataract. Disruptions of the Hsf4 gene cause lens defects in mice, indicating a requirement for HSF4 in fiber cell differentiation during lens development. However, neither the relationship between HSF4 and crystallins nor the detailed mechanism of maintenance of lens transparency by HSF4 is fully understood.


RESULTS
In an attempt to determine how the underlying biomedical and physiological mechanisms resulting from loss of HSF4 contribute to cataract formation, we generated an Hsf4 knockout mouse model. We showed that the Hsf4 knockout mouse (Hsf4-/-) partially mimics the human cataract caused by HSF4 mutations. Q-PCR analysis revealed down-regulation of several cataract-relevant genes, including gamma S-crystallin (Crygs) and lens-specific beaded filament proteins 1 and 2 (Bfsp1 and Bfsp2), in the lens of the Hsf4-/- mouse. Transcription activity analysis using the dual-luciferase system suggested that these cataract-relevant genes are the direct downstream targets of HSF4. The effect of HSF4 on gamma S-crystallin is exemplified by the cataractogenesis seen in the Hsf4-/-,rncat intercross. The 2D electrophoretic analysis of whole-lens lysates revealed a different expression pattern in 8-week-old Hsf4-/- mice compared with their wild-type counterparts, including the loss of some alpha A-crystallin modifications and reduced expression of gamma-crystallin proteins.


CONCLUSIONS
Our results indicate that HSF4 is sufficiently important to lens development and disruption of the Hsf4 gene leads to cataracts via at least three pathways: 1) down-regulation of gamma-crystallin, particularly gamma S-crystallin; 2) decreased lens beaded filament expression; and 3) loss of post-translational modification of alpha A-crystallin.
Shi
Xiaohe
X
Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences and Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200025, PR China. sxhiii@sina.com
Cui
Bin
B
Wang
Zhugang
Z
Weng
Lin
L
Xu
Zhongping
Z
Ma
Jinjin
J
Xu
Guotong
G
Kong
Xiangyin
X
Hu
Landian
L
D000818:Animals; D001483:Base Sequence; D002386:Cataract / Q000209:etiology* / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D017931:DNA Primers / Q000235:genetics; D004268:DNA-Binding Proteins / Q000172:deficiency* / Q000235:genetics; D004195:Disease Models, Animal; D015536:Down-Regulation; D005136:Eye Proteins / Q000235:genetics*; D005260:Female; D000076249:Heat Shock Transcription Factors; D006801:Humans; D007381:Intermediate Filament Proteins / Q000235:genetics*; D007908:Lens, Crystalline / Q000002:abnormalities / Q000254:growth & development / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009154:Mutation; D011247:Pregnancy; D011499:Protein Processing, Post-Translational; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000172:deficiency* / Q000235:genetics; D038202:alpha-Crystallin A Chain / Q000378:metabolism; D038222:gamma-Crystallins / Q000235:genetics*
C504673:Crygs protein, mouse; D017931:DNA Primers; D004268:DNA-Binding Proteins; D005136:Eye Proteins; D000076249:Heat Shock Transcription Factors; C484462:Hsf4 protein, mouse; D007381:Intermediate Filament Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; D038202:alpha-Crystallin A Chain; C079098:filensin; D038222:gamma-Crystallins; C084808:phakinin