Vanderbilt University, Department of Biological Sciences, Nashville, TN 37232, USA.
Dis Model Mech. 2011 Mar;4(2):255-67. doi: 10.1242/dmm.005587. Epub 2010 Oct 19.
Tuberous sclerosis complex (TSC) is an autosomal dominant disease caused by mutations in either the TSC1 (encodes hamartin) or TSC2 (encodes tuberin) genes. Patients with TSC have hamartomas in various organs throughout the whole body, most notably in the brain, skin, eye, heart, kidney and lung. To study the development of hamartomas, we generated a zebrafish model of TSC featuring a nonsense mutation (vu242) in the tsc2 gene. This tsc2(vu242) allele encodes a truncated Tuberin protein lacking the GAP domain, which is required for inhibition of Rheb and of the TOR kinase within TORC1. We show that tsc2(vu242) is a recessive larval-lethal mutation that causes increased cell size in the brain and liver. Greatly elevated TORC1 signaling is observed in tsc2(vu242/vu242) homozygous zebrafish, and is moderately increased in tsc2(vu242/+) heterozygotes. Forebrain neurons are poorly organized in tsc2(vu242/vu242) homozygous mutants, which have extensive gray and white matter disorganization and ectopically positioned cells. Genetic mosaic analyses demonstrate that tsc2 limits TORC1 signaling in a cell-autonomous manner. However, in chimeric animals, tsc2(vu242/vu242) mutant cells also mislocalize wild-type host cells in the forebrain in a non-cell-autonomous manner. These results demonstrate a highly conserved role of tsc2 in zebrafish and establish a new animal model for studies of TSC. The finding of a non-cell-autonomous function of mutant cells might help explain the formation of brain hamartomas and cortical malformations in human TSC.
结节性硬化症（TSC）是一种常染色体显性疾病，由 TSC1（编码错构瘤蛋白）或 TSC2（编码 tuberin）基因的突变引起。TSC 患者全身各器官均有错构瘤，尤以脑、皮肤、眼、心、肾和肺为甚。为了研究错构瘤的发生发展，我们构建了一种斑马鱼 TSC 模型，该模型在 tsc2 基因中存在无义突变（vu242）。该 tsc2（vu242）等位基因编码一种缺乏 GAP 结构域的截短型 tuberin 蛋白，而 GAP 结构域对于抑制 Rheb 和 TORC1 中的 TOR 激酶是必需的。我们发现 tsc2（vu242）是一种隐性的幼鱼致死突变，可导致大脑和肝脏细胞体积增大。在 tsc2（vu242/vu242）纯合子斑马鱼中观察到 TORC1 信号显著升高，在 tsc2（vu242/+）杂合子中适度升高。在 tsc2（vu242/vu242）纯合子突变体中，前脑神经元排列紊乱，灰质和白质广泛紊乱，异位细胞。遗传嵌合体分析表明，tsc2 以细胞自主的方式限制 TORC1 信号。然而，在嵌合体动物中，tsc2（vu242/vu242）突变细胞也以前脑非细胞自主的方式使野生型宿主细胞定位异常。这些结果证明了 tsc2 在斑马鱼中具有高度保守的作用，并建立了一种新的 TSC 动物模型。突变细胞的非细胞自主功能的发现可能有助于解释人类 TSC 中脑错构瘤和皮质畸形的形成。
