Novel allele of crybb2 in the mouse and its expression in the brain.
OBJECTIVE
O377 was identified as a new dominant cataract mutation in mice after radiation experiments. The purpose of this study was to genetically characterize the mutation and to analyze its biological consequences.


METHODS
Linkage analysis of the O377 mouse mutant was performed; candidate genes including Crybb2 were sequenced. The authors analyzed eyes and brains of the mutants by histology and the expression domains of Crybb2 by in situ hybridization and immunohistochemistry. RNA was isolated from whole brains of heterozygous and homozygous O377 mutants, and differential expression arrays were performed. All studies were compared with age- and strain-matched wild-type mice.


RESULTS
The mutation was mapped to chromosome 5 and characterized as an A-->T substitution at the end of intron 5 of the Crybb2 gene. It led to alternative splicing with a 57-bp insertion in the mRNA and to 19 additional amino acids in the protein. In the brain, betaB2-crystallin was expressed in the cerebellum, olfactory bulb, cerebral cortex, and hippocampus. The only morphologic difference in the brain is the increased number of Purkinje cells in the cerebellum of homozygous strain-matched mutants. Differential expression analysis revealed the upregulation of calpain-3 in the brain of homozygous mutants, which was confirmed by quantitative real-time PCR.


CONCLUSIONS
These results confirm the third allele of Crybb2 in the mouse that also affected exon 6 and the fourth Greek key motif. Moreover, expression analysis of Crybb2 identified for the first time distinct regions of expression in the brain, and the differential expression analysis points to the participation of Ca2+ in the corresponding pathologic processes.
Ganguly
Koustav
K
Institutes of Developmental Genetics, Helmholtz Center Munich, German Research Center for Environmental Health, Neuherberg, Germany.
Favor
Jack
J
Neuhäuser-Klaus
Angelika
A
Sandulache
Rodica
R
Puk
Oliver
O
Beckers
Johannes
J
Horsch
Marion
M
Schädler
Sandra
S
Vogt Weisenhorn
Daniela
D
Wurst
Wolfgang
W
Graw
Jochen
J
D000483:Alleles; D000818:Animals; D001921:Brain / Q000378:metabolism*; D002386:Cataract / Q000235:genetics*; D002874:Chromosome Mapping; D005260:Female; D015870:Gene Expression / Q000502:physiology*; D020869:Gene Expression Profiling; D017403:In Situ Hybridization; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D009154:Mutation; D020133:Reverse Transcriptase Polymerase Chain Reaction; D038206:beta-Crystallin B Chain / Q000235:genetics*
D038206:beta-Crystallin B Chain; C113634:beta-crystallin B2