Transcriptome Profiling Identifies Multiplexin as a Target of SAGA Deubiquitinase Activity in Glia Required for Precise Axon Guidance During Drosophila Visual Development.
The Spt-Ada-Gcn5 Acetyltransferase (SAGA) complex is a transcriptional coactivator with histone acetylase and deubiquitinase activities that plays an important role in visual development and function. In Drosophila melanogaster, four SAGA subunits are required for the deubiquitination of monoubiquitinated histone H2B (ubH2B): Nonstop, Sgf11, E(y)2, and Ataxin 7. Mutations that disrupt SAGA deubiquitinase activity cause defects in neuronal connectivity in the developing Drosophila visual system. In addition, mutations in SAGA result in the human progressive visual disorder spinocerebellar ataxia type 7 (SCA7). Glial cells play a crucial role in both the neuronal connectivity defect in nonstop and sgf11 flies, and in the retinal degeneration observed in SCA7 patients. Thus, we sought to identify the gene targets of SAGA deubiquitinase activity in glia in the Drosophila larval central nervous system. To do this, we enriched glia from wild-type, nonstop, and sgf11 larval optic lobes using affinity-purification of KASH-GFP tagged nuclei, and then examined each transcriptome using RNA-seq. Our analysis showed that SAGA deubiquitinase activity is required for proper expression of 16% of actively transcribed genes in glia, especially genes involved in proteasome function, protein folding and axon guidance. We further show that the SAGA deubiquitinase-activated gene Multiplexin (Mp) is required in glia for proper photoreceptor axon targeting. Mutations in the human ortholog of Mp, COL18A1, have been identified in a family with a SCA7-like progressive visual disorder, suggesting that defects in the expression of this gene in SCA7 patients could play a role in the retinal degeneration that is unique to this ataxia.
Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907.
Jingqun
0000-0002-0079-6323
J
Ma
Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907.
Kaelan J
KJ
Brennan
Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907.
Mitch R
MR
D'Aloia
Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907 Purdue University Libraries, Purdue University, West Lafayette, Indiana 47907 Purdue University Center for Cancer Research, Purdue University, West Lafayette, Indiana 47907.
Pete E
0000-0002-9316-4404
PE
Pascuzzi
Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907 Purdue University Center for Cancer Research, Purdue University, West Lafayette, Indiana 47907 vweake@purdue.edu.
Vikki M
0000-0002-5933-9952
VM
Weake
D000123:Acetyltransferases / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence / Q000235:genetics; D000818:Animals; D000071437:Axon Guidance / Q000235:genetics; D011508:Chondroitin Sulfate Proteoglycans / Q000235:genetics* / Q000378:metabolism; D003094:Collagen / Q000235:genetics* / Q000378:metabolism; D024102:Collagen Type VIII / Q000235:genetics*; D043170:Collagen Type XVIII; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism; D004331:Drosophila melanogaster / Q000235:genetics / Q000254:growth & development; D005123:Eye / Q000254:growth & development* / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D006657:Histones / Q000235:genetics; D006801:Humans; D009154:Mutation; D009457:Neuroglia / Q000378:metabolism; D012162:Retinal Degeneration / Q000235:genetics / Q000473:pathology; D020754:Spinocerebellar Ataxias / Q000235:genetics / Q000473:pathology; D059467:Transcriptome / Q000235:genetics*
C000612902:COL18A1 protein, human; D011508:Chondroitin Sulfate Proteoglycans; D024102:Collagen Type VIII; D043170:Collagen Type XVIII; D029721:Drosophila Proteins; D006657:Histones; C567943:Mp protein, Drosophila; D003094:Collagen; D000123:Acetyltransferases
SAGA; SCA7; axon guidance; glia; histone ubiquitination