Diencephalic Size Is Restricted by a Novel Interplay Between GCN5 Acetyltransferase Activity and Retinoic Acid Signaling.
Diencephalic defects underlie an array of neurological diseases. Previous studies have suggested that retinoic acid (RA) signaling is involved in diencephalic development at late stages of embryonic development, but its roles and mechanisms of action during early neural development are still unclear. Here we demonstrate that mice lacking enzymatic activity of the acetyltransferase GCN5 ((Gcn5hat/hat)), which were previously characterized with respect to their exencephalic phenotype, exhibit significant diencephalic expansion, decreased diencephalic RA signaling, and increased diencephalic WNT and SHH signaling. Using a variety of molecular biology techniques in both cultured neuroepithelial cells treated with a GCN5 inhibitor and forebrain tissue from (Gcn5hat/hat) embryos, we demonstrate that GCN5, RARα/γ, and the poorly characterized protein TACC1 form a complex in the nucleus that binds specific retinoic acid response elements in the absence of RA. Furthermore, RA triggers GCN5-mediated acetylation of TACC1, which results in dissociation of TACC1 from retinoic acid response elements and leads to transcriptional activation of RA target genes. Intriguingly, RA signaling defects caused byin vitroinhibition of GCN5 can be rescued through RA-dependent mechanisms that require RARβ. Last, we demonstrate that the diencephalic expansion and transcriptional defects seen in (Gcn5hat/hat) mutants can be rescued with gestational RA supplementation, supporting a direct link between GCN5, TACC1, and RA signaling in the developing diencephalon. Together, our studies identify a novel, nonhistone substrate for GCN5 whose modification regulates a previously undescribed, tissue-specific mechanism of RA signaling that is required to restrict diencephalic size during early forebrain development.SIGNIFICANCE STATEMENTChanges in diencephalic size and shape, as well as SNPs associated with retinoic acid (RA) signaling-associated genes, have been linked to neuropsychiatric disorders. However, the mechanisms that regulate diencephalic morphogenesis and the involvement of RA signaling in this process are poorly understood. Here we demonstrate a novel role of the acetyltransferase GCN5 in a previously undescribed mechanism of RA signaling in the developing forebrain that is required to maintain the appropriate size of the diencephalon. Together, our experiments identify a novel nonhistone substrate of GCN5, highlight an essential role for both GCN5 and RA signaling in early diencephalic development, and elucidate a novel molecular regulatory mechanism for RA signaling that is specific to the developing forebrain.
Graduate Program in Cell Biology, Stem Cells, and Development, University of Colorado Denver, Aurora, Colorado 80045, lee.niswander@ucdenver.edu wildej@mit.edu.|Department of Pediatrics, Section of Developmental Biology, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, Colorado 80045, and.
Jonathan J
0000-0002-0800-8854
JJ
Wilde
Department of Pediatrics, Section of Developmental Biology, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, Colorado 80045, and.
Julie A
JA
Siegenthaler
University of Texas M.D. Anderson Cancer Center, Department of Epigenetics and Molecular Carcinogenesis, Smithville, Texas 78957.
Sharon Y R
0000-0002-4824-3269
SY
Dent
Department of Pediatrics, Section of Developmental Biology, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, Colorado 80045, and lee.niswander@ucdenver.edu wildej@mit.edu.
Lee A
LA
Niswander
D000818:Animals; D004027:Diencephalon / Q000033:anatomy & histology* / Q000196:embryology / Q000378:metabolism*; D004789:Enzyme Activation; D005260:Female; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009929:Organ Size / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D014212:Tretinoin / Q000378:metabolism*; D050880:p300-CBP Transcription Factors / Q000378:metabolism*; D000099224:p300-CBP-Associated Factor
D014212:Tretinoin; D050880:p300-CBP Transcription Factors; D000099224:p300-CBP-Associated Factor
GCN5; KAT2A; TACC1; diencephalon; retinoic acid; thalamus