Gene expression analysis of photoreceptor cell loss in bbs4-knockout mice reveals an early stress gene response and photoreceptor cell damage.
OBJECTIVE
To identify and characterize gene expression changes associated with photoreceptor cell loss in a Bbs4-knockout mouse model of retinal degeneration.


METHODS
Differential gene expression in the eyes of 5-month-old Bbs4(-/-) mice undergoing retinal degeneration were analyzed using gene microarrays (Affymetrix, Santa Clara, CA). Elevated ocular transcripts were confirmed by Northern blotting of RNA from Bbs4(-/-) and three additional mouse models of Bardet-Biedl Syndrome (BBS). TUNEL assays and transmission electron microscopy were used to study cell death and photoreceptor morphology in these mice.


RESULTS
Three hundred fifty-four probes were differentially expressed in Bbs4(-/-) eyes compared with controls using a twofold cutoff. Numerous vision-related transcripts decreased because of photoreceptor cell loss. Increased expression of the stress response genes Edn2, Lcn2, Serpina3n, and Socs3 was noted at 5 months of age and as early as postnatal week 4 in the eyes of four BBS mouse model strains. A burst of apoptotic activity in the photoreceptor outer nuclear layer at postnatal week 2 and highly disorganized outer segments by postnatal weeks 4 to 6 was observed in all four strains.


CONCLUSIONS
The specific loss of photoreceptors in Bbs4(-)(/)(-) mice allows us to identify a set of genes that are preferentially expressed in photoreceptors compared with other cell types found in the eye and is a valuable resource in the continuing search for genes involved in retinal disease. The molecular and morphologic changes observed in young BBS animal model eyes implies that BBS proteins play a critical, early role in establishing the correct structure and function of photoreceptors.
Swiderski
Ruth E
RE
Department of Pediatrics, University of Iowa, Iowa City, Iowa 52242, USA.
Nishimura
Darryl Y
DY
Mullins
Robert F
RF
Olvera
Marissa A
MA
Ross
Jean L
JL
Huang
Jian
J
Stone
Edwin M
EM
Sheffield
Val C
VC
D000209:Acute-Phase Proteins / Q000235:genetics*; D000818:Animals; D017209:Apoptosis; D020788:Bardet-Biedl Syndrome / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D015152:Blotting, Northern; D019333:Endothelin-2 / Q000235:genetics; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D020287:In Situ Nick-End Labeling; D000071068:Lipocalin-2; D054834:Lipocalins; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008869:Microtubule-Associated Proteins / Q000235:genetics*; D020411:Oligonucleotide Array Sequence Analysis; D015513:Oncogene Proteins / Q000235:genetics; D020419:Photoreceptor Cells, Vertebrate / Q000378:metabolism* / Q000473:pathology; D012162:Retinal Degeneration / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D015843:Serpins / Q000235:genetics; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins / Q000235:genetics
D000209:Acute-Phase Proteins; C506281:BBS4 protein, mouse; D019333:Endothelin-2; D000071068:Lipocalin-2; D054834:Lipocalins; D008869:Microtubule-Associated Proteins; D015513:Oncogene Proteins; C516624:Serpina3n protein, mouse; D015843:Serpins; C491411:Socs3 protein, mouse; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; C071332:Lcn2 protein, mouse