Genetic architecture of murine skin inflammation and tumor susceptibility

Gene expression in self-renewing epithelial tissues is controlled by cis- and trans-activating regulatory factors that mediate responses to exogenous agents capable of causing tissue damage, infection, inflammation, or tumorigenesis. We used network construction methods to analyze the genetic architecture of gene expression in normal mouse skin in a cross between tumor-susceptible Mus musculus and tumor-resistant Mus spretus. We demonstrate that gene expression motifs representing different constituent cell types within the skin such as hair follicle cells, haematopoietic cells, and melanocytes are under separate genetic control. Motifs associated with inflammation, epidermal barrier function and proliferation are differentially regulated in mice susceptible or resistant to tumor development. The intestinal stem cell marker Lgr5 is identified as a candidate master regulator of hair follicle gene expression, and the Vitamin D receptor (Vdr) links epidermal barrier function, inflammation, and tumor susceptibility. Keywords: Expression Quantitative Trait Loci A backcross was generated using male Mus spretus and female FVB/N mice; female F1 hybrids were mated with male FVB/N mice. Seventy-one backcross mice (8-12 weeks old) received a single dose of DMBA (25 µg per mouse in 200 µl acetone). Starting one week after the initiation tumors were promoted with TPA (200 µl of 10-4 M solution in acetone) twice weekly for 20 weeks. Initiation and promotion were performed on dorsal back skin. Normal tail skin was snap frozen when the animals were sacrificed. Tail epidermis from completely untreated Spretus, FVB, and Spretus x FVB F1 mice was also analyzed.自我更新上皮组织的基因表达由顺式（cis-）与反式（trans-）激活调控因子所调控，这类因子可介导机体对可引发组织损伤、感染、炎症或肿瘤发生的外源性刺激的应答反应。本研究采用网络构建方法，分析了肿瘤易感型小家鼠（Mus musculus）与肿瘤抵抗型小家鼠（Mus spretus）杂交背景下正常小鼠皮肤的基因表达遗传架构。本研究证实，代表皮肤内不同组成细胞类型（如毛囊细胞、造血细胞与黑素细胞）的基因表达特征基序（gene expression motifs）受独立的遗传调控。与炎症、表皮屏障功能及细胞增殖相关的特征基序，在肿瘤易感与抵抗型小鼠中呈现差异化调控模式。肠道干细胞标志物Lgr5被鉴定为毛囊基因表达的候选主调控因子，而维生素D受体（Vitamin D receptor, Vdr）则关联了表皮屏障功能、炎症反应与肿瘤易感性。 关键词：表达数量性状基因座（Expression Quantitative Trait Loci） 本研究以雄性Mus spretus与雌性FVB/N小鼠杂交获得F1代杂合子，随后将雌性F1杂合子与雄性FVB/N小鼠回交，构建回交群体。共获得71只8~12周龄的回交小鼠，对其给予单次DMBA给药处理：每只小鼠以200 μl丙酮溶解25 μg DMBA进行处理。于肿瘤启动给药一周后，每周两次以TPA（200 μl浓度为10^-4 M的丙酮溶液）进行肿瘤促进处理，持续20周。肿瘤启动与促进操作均于背部皮肤进行。实验动物处死后，将正常尾部皮肤快速冷冻保存。同时对完全未接受任何处理的Spretus、FVB以及Spretus × FVB F1小鼠的尾部表皮组织进行了分析。