Department of Neurobiology, University of California-Davis, Davis, CA, USA.
Physiol Genomics. 2011 Sep 22;43(18):1049-55. doi: 10.1152/physiolgenomics.00134.2010. Epub 2011 Jul 5.
We previously identified a region of mouse chromosome 7 that influences body fat mass in F2 littermates of congenic × background intercrosses. Current analyses revealed that alleles in the donor region of the subcongenic B6.C-D7Mit318 (318) promoted a twofold increase in adiposity in homozygous lines of 318 compared with background C57BL/6ByJ (B6By) mice. Parent-of-origin effects were discounted through cross-fostering studies and an F1 reciprocal cross. Mapping of the donor region revealed that it has a maximal size of 2.8 Mb (minimum 1.8 Mb) and contains a maximum of eight protein coding genes. Quantitative PCR in whole brain, liver, and gonadal white adipose tissue (GWAT) revealed differential expression between genotypes for three genes in females and two genes in males. Alpha-2,8-sialyltransferase 8B (St8sia2) showed reduced 318 mRNA levels in brain for females and males and in GWAT for females only. Both sexes of 318 mice had reduced Repulsive guidance molecule-a (Rgma) expression in GWAT. In brain, Family with sequence similarity 174 member b (Fam174b) had increased expression in 318 females, whereas Chromodomain helicase DNA binding protein 2 (Chd2-2) had reduced expression in 318 males. No donor region genes were differentially expressed in liver. Sequence analysis of coding exons for all genes in the 318 donor region revealed only one single nucleotide polymorphism that produced a nonsynonymous missense mutation, Gln7Pro, in Fam174b. Our findings highlight the difficulty of using expression and sequence to identify quantitative trait genes underlying obesity even in small genomic regions.
我们之前已经确定了影响 F2 同窝仔鼠体脂量的小鼠 7 号染色体区域。目前的分析显示，来自亚纯合 B6.C-D7Mit318（318）供体区域的等位基因，使 318 纯合子鼠的肥胖程度增加了两倍，而与背景 C57BL/6ByJ（B6By）鼠相比。通过交叉寄养研究和 F1 回交，排除了亲本来源的影响。供体区域的作图显示，它的最大大小为 2.8Mb（最小 1.8Mb），包含最多 8 个蛋白编码基因。对全脑、肝脏和性腺白色脂肪组织（GWAT）的定量 PCR 显示，在女性和男性中，3 个基因和 2 个基因在基因型之间存在差异表达。α-2,8-唾液酸转移酶 8B（St8sia2）在女性和男性的大脑和 GWAT 中以及女性的 GWAT 中显示出 318mRNA 水平降低。318 鼠的两种性别在 GWAT 中的 Repulsive guidance molecule-a（Rgma）表达减少。在大脑中，Family with sequence similarity 174 member b（Fam174b）在 318 雌性中表达增加，而 Chromodomain helicase DNA binding protein 2（Chd2-2）在 318 雄性中表达减少。在肝脏中，没有供体区域基因表达差异。对 318 供体区域的所有基因的编码外显子进行序列分析，只发现一个单核苷酸多态性，导致 Fam174b 产生一个非 synonymous错义突变，Qln7Pro。我们的发现强调了即使在小的基因组区域，使用表达和序列来鉴定肥胖相关的数量性状基因也很困难。
