The MYST-Containing Protein Chameau Is Required for Proper Sensory Organ Specification during Drosophila Thorax Morphogenesis

The adult thorax of Drosophila melanogaster is covered by a stereotyped pattern of mechanosensory bristles called macrochaetes. Here, we report that the MYST containing protein Chameau (Chm) contributes to the establishment of this pattern in the most dorsal part of the thorax. Chm mutant pupae present extra-dorsocentral (DC) and scutellar (SC) macrochaetes, but a normal number of the other macrochaetes. We provide evidences that chm restricts the singling out of sensory organ precursors from proneural clusters and genetically interacts with transcriptional regulators involved in the regulation of achaete and scute in the DC and SC proneural cluster. This function of chm likely relies on chromatin structure regulation since a protein with a mutation in the conserved catalytic site fails to rescue the formation of supernumerary DC and SC bristles in chm mutant flies. This is further supported by the finding that mutations in genes encoding chromatin modifiers and remodeling factors, including Polycomb group (PcG) and Trithorax group (TrxG) members, dominantly modulate the penetrance of chm extra bristle phenotype. These data support a critical role for chromatin structure modulation in the establishment of the stereotyped sensory bristle pattern in the fly thorax

Contrôle de la morphogenèse chez Drosophila melanogaster (Rôle de chameau, une acétyltransférase putative impliquée dans les mécanismes épigenetiques de répression transcriptionnelle)

AIX-MARSEILLE2-BU Sci.Luminy (130552106) / SudocSudocFranceF

Chameau HAT and DRpd3 HDAC function as antagonistic cofactors of JNK/AP-1-dependent transcription during Drosophila metamorphosis

Gene regulation by AP-1 transcription factors in response to Jun N-terminal kinase (JNK) signaling controls essential cellular processes during development and in pathological situations. Here, we report genetic and molecular evidence that the histone acetyltransferase (HAT) Chameau and the histone deacetylase DRpd3 act as antagonistic cofactors of DJun and DFos to modulate JNK-dependent transcription during thorax metamorphosis and JNK-induced apoptosis in Drosophila. We demonstrate in cultured cells that DFos phosphorylation mediated by JNK signaling plays a central role in coordinating the dynamics of Chameau and DRpd3 recruitment and function at AP-1-responsive promoters. Activating the pathway stimulates the HAT function of Chameau, promoting histone H4 acetylation and target gene transcription. Conversely, in response to JNK signaling inactivation, DRpd3 is recruited and suppresses histone acetylation and transcription. This study establishes a direct link among JNK signaling, DFos phosphorylation, chromatin modification, and AP-1-dependent transcription and its importance in a developing organism

<i>chm</i> does not genetically interacts with mutants of the Notch pathway during DC and SC macrochaete development.

<p>Bristle scoring was compared using Student's <i>t</i> test.</p>*<p>, statistically different compared to <i>chm</i> null flies, <i>P</i><0.05.</p><p>ns, not statistically different with regards to <i>chm</i> mutant flies. N, number of thoraces examined. DC: dorsocentral bristles, SC: scutellar bristles.</p

<i>chm</i> controls SOP singling out from proneural clusters.

<p>(A) Scutellar parts of the posterior notum of wing imaginal discs from a WT late third instar larva (left panel) and from a <i>chm</i> mutant white pupa (right panel) stained for SOPs using the <i>neur^A101</i> LacZ enhancer trap strain. The arrow indicates an ectopic SOP singling out in the chm mutant disc. (B) Phenotypic rescue of <i>chm</i> mutant supernumerary bristle phenotype upon providing Chm back in <i>pnr</i>, <i>sca</i> and <i>neur</i> expression domains, and in the proximal part of the notum (MZ980). Bristle scoring was compared using Student's <i>t</i> test: *, statistically different with regards to <i>chm</i> mutant flies, <i>P</i><0.05; ns, not statistically different. N, number of thoraces examined. s.e.m of 3 independent experiment is indicated (C) Extra-SOPs in <i>chm</i> mutants required ac/sc transcription. N, number of thoraces examined.</p

<i>kay</i>, <i>hep</i> or <i>jra/Djun</i> do not dominantly interact with <i>chm</i> during DC and SC macrochaete development.

<p>Bristle scoring was compared using Student's <i>t</i> test. ns, not statistically different with regards to <i>chm</i> mutant flies. N, number of thoraces examined.</p>#<p>, total number of individuals scored for this genotype by pulling data from different independent crosses.</p><p>DC: dorsocentral bristles, SC: scutellar bristles.</p

The MYST domain acetyltransferase Chameau functions in epigenetic mechanisms of transcriptional repression.

International audienceReversible acetylation of histone tails plays an important role in chromatin remodelling and regulation of gene activity. While modification by histone acetyltransferase (HAT) is usually linked to transcriptional activation, we provide here evidence for HAT function in several types of epigenetic repression. Chameau (Chm), a new Drosophila member of the MYST HAT family, dominantly suppresses position effect variegation (PEV), is required for the maintenance of Hox gene silencing by Polycomb group (PcG) proteins, and can partially substitute for the MYST Sas2 HAT in yeast telomeric position effect (TPE). Finally, we provide in vivo evidence that the acetyltransferase activity of Chm is required in these processes, since a variant protein mutated in the catalytic domain no longer rescues PEV modification, telomeric silencing of SAS2-deficient yeast cells, nor lethality of chm mutant flies. These findings emphasize the role of an acetyltransferase in gene silencing, which supports, according to the histone code hypothesis, that transcription at a particular locus is determined by a precise combination of histone tail modifications rather than by overall acetylation levels

Chm epigenetically controls macrochaete formation.

<p>(A) Chm putative HAT activity is required for SOP determination: No rescue of <i>chm</i> extra bristle phenotype upon expression of the Chm^G680 variant in DC and SC proneural clusters (<i>sca</i>-Gal4; <i>pnr</i>-Gal4). (B) Summary of genetic interactions between <i>chm</i> and 16 genes encoding chromatin remodeling factors. No change in DC or SC bristle number was observed in heterozygotes for each of the 16 genes, except for <i>ash1⁶/+</i> and <i>tara^EP(3)3463/+</i> which exhibit 4.07 and 4.18 DC, respectively, and a normal number of 4 SC. Molecular function of each factor is given. Bristle scoring were compared using Student's <i>t</i> test: *, statistically different with regards to <i>chm</i> mutant flies, <i>P</i><0.05; ns, not statistically different. N, number of thoraces examined.</p

<i>chm</i> is required for the development of proper number of aDC and aSC macrochaetes.

<p>(A) Cuticle preparation of WT and <i>chm</i> pharate adult thoraces. White arrows point towards supernumerary aSC bristles with their proper socket cells, and the asterix to the thoracic cleft induced by <i>chm</i> mutation. aDC: anterior DC, pDC: posterior DC, aSC: anterior SC, pSC: posterior SC. (B) Summary of the genetic characterization of <i>chm</i> mutant bristle phenotype, and phenotypic rescue by UAS-<i>chm</i>. Bristle scoring were compared using Student's <i>t</i> test: *, statistically different with regards to WT flies, <i>P</i><0.05. N, number of thoraces examined. z-, zygotic mutant. m-, z-, maternal and zygotic mutant, s.e.m of 3 independent experiment is indicated.</p