Elucidating the mechanisms by which ectopically expressed genes and piRNAs perturb somatic cell function when histone methylation is inappropriately regulated

项目摘要 歌舞伎样综合征是一种神经发育障碍，由H3 K4脱甲基酶LSD 1突变引起， 其特征在于一系列异常的躯体表型，包括智力残疾、颅面畸形、 异常和发育迟缓。尽管它们与歌舞伎样综合征有关， 神经发育综合征，组蛋白修饰酶如LSD 1的突变如何导致复杂的神经发育综合征， 发育表型尚不清楚。为了更好地了解组蛋白修饰酶的突变如何影响 体细胞发育我们已经开发出一个C.缺失SPR-5的秀丽隐杆线虫模型，C. LSD 1的线虫直系同源物， 除了组蛋白3赖氨酸9（H3 K9）甲基转移酶MET-2之外。在没有SPR-5和MET-2的情况下， 在体细胞组织中异位表达生殖系基因，导致表型类似于在 神经发育综合征，包括肌肉缺陷和发育迟缓。引人注目的是， SPR-5、Met-2突变体中候选生殖系基因的发育延迟和异位表达可 通过敲低H3 K36甲基转移酶MES-4来拯救，MES-4标记了生殖系基因， 在下一代的生殖细胞中重新表达。这些数据表明，发育迟缓，我们 观察到在SPR-5和MET-2缺失的情况下， 组织中在MES-4调节的生殖系基因座中，在spr-5的索马中异位表达; met-2 突变体，我们检测PIWI相互作用RNA或piRNA，以及调节其功能的基因。piRNA是一种 大类小的非编码RNA，通过在几种不同的途径中发挥作用来调节发育， 包括表观遗传编程、生殖系转录沉默、RNA周转和翻译控制。异位 最近，piRNA基因的表达与体细胞发育和疾病有关，但如何异位表达piRNA基因， piRNA在体细胞中起作用，或者它们是否导致了尚不清楚的异常发育表型。 因此，我们的新C。elegans模型提供了一个独特的机会，从分子上证明异位生殖系 基因和皮尔纳表达影响正常发育。通过结合尖端的大型基因组实验， 经典的发育技术和单分子荧光原位杂交，我们将使用我们的C。 elegans模型，以确定异位生殖系基因如何改变体细胞基因表达，2）定义组织 异位生殖系基因表达的特异性，和3）检查不同的染色质状态如何有助于 体细胞组织中生殖系基因的错误表达。在AIM 2中，我们将采用类似的方法来检查 piRNA的异位表达如何促成组织特异性体细胞缺陷。共同提出的目标 将提供这些异位转录事件，当组蛋白修饰 酶发生突变，导致与人类神经发育中所见的表型重叠的表型。 紊乱

PROJECT SUMMARY Kabuki-like syndrome is a neurodevelopmental disorder caused by mutations in the H3K4 demethylase, LSD1, and is characterized by a range of abnormal somatic phenotypes including intellectual disabilities, craniofacial abnormalities, and developmental delay. Despite their implication in Kabuki-like syndrome, and other neurodevelopmental syndromes, how mutations in histone modifying enzymes like LSD1 contribute to complex developmental phenotypes is unclear. To better understand how mutations in histone modifying enzymes affect somatic development we have developed a C. elegans model lacking SPR-5, the C. elegans ortholog of LSD1, in addition to the histone 3 lysine 9 (H3K9) methyltransferase MET-2. Without SPR-5 and MET-2, progeny ectopically express germline genes in somatic tissues leading to phenotypes that resemble those observed in neurodevelopmental syndromes, including muscle defects and developmental delay. Strikingly, the developmental delay and ectopic expression of candidate germline genes in spr-5; met-2 mutants can be rescued by knocking down the H3K36 methyltransferase, MES-4, which bookmarks germline genes for reexpression in the germline of the next generation. These data suggest that the developmental delay that we observe in the absence of SPR-5 and MET-2 is caused by ectopic expression of germline genes in somatic tissues. Among the MES-4 regulated germline loci that are ectopically expressed in the soma of spr-5; met-2 mutants, we detect PIWI-interacting RNAs, or piRNAs, and the genes that regulate their function. piRNAs are a large class of small non-coding RNAs that regulate development by functioning in several different pathways, including epigenetic programming, germline transcript silencing, RNA turnover, and translational control. Ectopic expression of piRNA genes has recently been implicated in somatic development and diseases, but how ectopic piRNAs function in somatic cells or if they contribute to abnormal developmental phenotypes poorly understood. Thus, our new C. elegans model provides a unique opportunity to molecularly demonstrate how ectopic germline gene and piRNA expression affects normal development. By combining cutting-edge large genomic experiments, classical developmental techniques, and single molecule fluorescent in situ hybridization we will use our C. elegans model in AIM 1 to determine how ectopic germline genes alter somatic gene expression, 2) define tissue specificity of ectopic germline gene expression, and 3) examine how distinct chromatin states contribute to misexpression of germline genes in somatic tissues. In AIM 2, we will employ similar approaches to examine how ectopic expression of piRNAs contributes to tissue specific somatic defects. Together, the proposed aims will provide mechanistic insight into how these ectopic transcriptional events, that occur when histone modifying enzymes are mutated, contribute to phenotypes that overlap with those seen in human neurodevelopmental disorders.