ROLE OF LDB1-LMX1B TRANSCRIPTION FACTOR COMPLEX IN CALVARIA DEVELOPMENT

描述（由申请人提供）：颅骨（颅骨的上部）由骨板和纤维关节（骨缝和）组成，这两个组成部分之间的平衡对于颅骨的正常发育至关重要。颅骨畸形是人类最常见的出生缺陷之一;颅缝早闭（过早失去缝）导致颅骨畸形，也会影响大脑和口面发育。目前颅骨缺损的治疗通常涉及侵入性和重复性手术，并发症的风险相对较高，因此必须改进干预方法。全面了解颅骨发育的分子遗传调控对于设计诊断、治疗和预防相关出生缺陷的创新方法至关重要。我们研究的长期目标是通过识别对这一过程重要的因素并确定它们之间的关系来表征颅骨发育的基因调控网络。根据我们的初步结果，LDB 1（LIM结构域结合蛋白1），一个转录辅因子，在颅骨发育中起着至关重要的作用;失活 小鼠头部间充质和一些周围组织中Ldb 1的表达导致颅顶处异位骨形成，代替了<$门和部分骨缝，模拟颅缝早闭。此外，早期的一份报告显示，在人类指甲-髌骨综合征基因Lmx 1b（LIM同源框转录因子1b）的小鼠突变体中存在类似的缺陷，这表明LDB 1和LMX 1B可能是这种情况下的伴侣。然而，Ldb 1和Lmx 1b调节颅骨发育的分子和细胞机制仍然未知。因此，这项研究的目的是i）描述Ldb 1在calvari发育中的功能，ii）确定Lmx 1b是否确实是Ldb 1的伴侣。我们将使用小鼠突变模型以及细胞培养和器官培养系统来确定Ldb 1和Lmx 1b突变引起的形态学、细胞和分子变化。这项研究的结果将为颅骨发育的遗传调控提供新的见解，并将Ldb 1和Lmx 1b确定为人类颅骨出生缺陷（如颅缝早闭）的重要参与者。

DESCRIPTION (provided by applicant): The calvaria (upper part of the skull) comprises plates of bone and fibrous joints (sutures and fontanelles), and the balance between the two components is essential for normal development of the calvaria. Calvarial malformation is among the most common birth defects in humans; craniosynostosis (premature loss of suture(s)) leads to a dysmorphic skull and can also affect brain and orofacial development. Current treatment of calvarial defects often involves invasive and repetitive surgeries with relatively high risks for complications, and thus improving the methods of intervention is imperative. Comprehensive understanding of the molecular genetic regulation of calvaria development is crucial to devising innovative methods for diagnosis, treatment, and prevention of related birth defects. The long-term goal of our research is to characterize the gene regulatory network of calvaria development, by identifying factors important for this process and determining their relationship. Based on our preliminary results, LDB1 (LIM-domain binding protein 1), a transcription cofactor, plays an essential role in calvaria development; inactivation of Ldb1 in head mesenchyme and some of the surrounding tissues in mice led to ectopic bone formation at the vertex in place of a fontanelle and parts of the sutures, mimicking craniosynostosis. In addition, an earlier report showed a similar defect in mouse mutants of human Nail-Patella syndrome gene, Lmx1b (LIM homeobox transcription factor 1b), which suggests that LDB1 and LMX1B may be partners in this context. However, molecular and cellular mechanisms by which Ldb1 and Lmx1b regulate calvaria development remain unknown. Therefore, the goal of this research proposal is i) to characterize the function of Ldb1 in calvari development, and ii) determine whether Lmx1b is indeed the partner of Ldb1 for this specific role. We will use mouse mutant models as well as cell culture and organ culture systems to determine the morphological, cellular and molecular changes resulting from the mutation of Ldb1 and Lmx1b. The outcome of this research will provide novel insights into the genetic regulation of calvaria development, and establish Ldb1 and Lmx1b as important players in human calvarial birth defects such as craniosynostosis.