Mechanisms of Pituitary Development

描述(由申请人提供)：在胎儿发育过程中，从全垂体功能减退(完全丧失功能)到失去单一激素分泌群体的垂体缺陷并不少见，其中最常见的单一激素缺陷是生长激素缺失，影响每4000名新生儿中就有一名。在Rathke氏囊(垂体岛)形成之前，对雏鸡和其他模型系统早期假定的腺垂体(垂体腺)的起源和模式形成机制的研究是非常有限的、不确定的和相互矛盾的。发育中的鸡腺垂体是研究胚胎发生过程中外胚层原基复杂的时空模式事件、组织相互作用和信号机制的良好模型系统。使用多种荧光染料和延时视频显微镜的高分辨率命运图谱，以及使用原位杂交(ISH)对基因表达模式的详细空间和时间分析，将被用于最终确定形成腺垂体的外胚层细胞的神经/非神经起源。然后，为了确定形成腺垂体的外胚层细胞群体的指定时间和范围，以及导致指定的诱导性组织相互作用，将个别候选组织培养在胶原凝胶中。在培养后使用一些标记基因的ISH将阐明自神经化开始时胚胎中起作用的组织群体的特定状态。然后，在胶原凝胶中培养的组织重组将被用来研究导致规范的诱导性组织相互作用。最后，我们将探讨决定细胞对腺垂体命运的分子机制。初步研究发现了一条与腺垂体细胞特性有关的新途径，即胰岛素/胰岛素样生长因子途径。在分别用ISH和免疫细胞化学对胰岛素家族成员的基因表达和蛋白质分布进行详细分析后，我们将使用获得和功能丧失的方法进行实验，以开始阐明腺垂体的一系列信号事件所涉及的分子机制。

DESCRIPTION (provided by applicant): Pituitary defects ranging from panhypopituitarism (total loss of function) to loss of a single hormone secreting population are not uncommon in fetal development, with the most frequent single hormone deficiency, loss of growth hormone, affecting 1 in 4000 newborns. Studies on the origin and patterning mechanisms of the early presumptive adenohypophysis (anterior pituitary gland) in chick and other model systems, prior to formation of Rathke's pouch (the pituitary anlage), are highly limited, inconclusive and contradictory. The developing chick adenohypophysis is an excellent model system to study the complex temporal and spatial patterning events, tissue interactions and signaling mechanisms that occur in ectodermal primordia during embryogenesis. High-resolution fate mapping, using multiple fluorescent dyes and time-lapse videomicroscopy, together with detailed spatial and temporal analyses of gene expression patterns, using in situ hybridization (ISH), will be used to determine conclusively the neural/non-neural origins of the ectodermal cells that form the adenohypophysis. Then, to establish the timing and extent of specification of the populations of ectodermal cells that form the adenohypophysis, and the inductive tissue interactions that lead to specification, individual candidate tissues will be cultured in collagen gels. ISH using a number of marker genes following culture will elucidate the state of specification of the contributing tissue populations in embryos from the beginning of neuralization. Tissue recombinants cultured in collagen gels then will be used to investigate the inductive tissue interactions leading to specification. Lastly, the molecular mechanisms responsible for the specification of cells to an adenohypophyseal fate will be investigated. Preliminary studies implicate a novel pathway involved in adenohypophyseal cell specification, the Insulin/Insulin-like Growth Factor pathway. Following detailed analyses of gene expression and protein distribution, by ISH and immunocytochemistry, respectively, of Insulin family members, we will conducts experiments using both gain and loss of function approaches to begin to elucidate the molecular mechanisms involved in the sequential signaling events underlying specification of the adenohypophysis.