Identification of genes involved in genomic imprinting and intrauterine growth

Silver-Russell综合征(SRS)致病区域鉴定及候选基因分析：对1例核型异常的SRS患者进行微卫星等位基因分析，发现7p13-q11片段为双等位基因，其余7号染色体区域仅为母系等位基因。结果表明，可能的SRS区域局限于7q11-QTER。虽然7号染色体上的两个基因GRB10和MEST已成为SRS的候选基因，但利用杂交细胞板对gents进行印迹分析和甲基化分析的结果并不支持这一假设。1.2-Mb PAC重叠群(物理和转录图谱)的构建：为了确认7q32上的印迹基因簇，构建了包含MEST的D7S530 wAD7S649之间的重叠群。7q32印记基因鉴定：在重叠群定位的基因中，包括MEST、COPG2、COPG2TT1(Cftl)、KIAA0265、CPA3、CPA1、mdTSGA14。MEST和COPG2IT1都是父系表达的，而CPA3是母系表达的，尽管COPG2被认为是父系表达的，但它实际上是双等位表达的。然而，一种新的EST(COPG2IT1)，即COPG2-内含子20的反义转录本，在胎儿组织中显示了父系单等位基因的表达。CPA3在胎心、肾、肺和成人前列腺中有部分印迹，而在淋巴母细胞中部分或完全失去印迹。COPG2、KIAA0265、CPA1和TSGA14均表现为双等位基因表达，不支持其印记。这些发现，特别是位于MEST附近的COPG2和TSGA14没有印记，表明7q32区域不是严格控制的印记结构域，而是由独立的印记信号控制的。

Identification of Silver-Russell syndrome (SRS) responsible region and candidate gene analysis : Allelotype analysis of one SRS patient with abnormal karyotype using microsatellite markers revealed that a 7p13-q11 segment showed biallelism while the remaining region of chromosome 7 showed only maternal alleles. The results indicated that the putative SRS region is confined to 7q11-qter. Although two genes on chromosohie 7, GRB10 and MEST, have become a candidate gene for SRS, results of an imprinting analysis of the gents using hybrid cell panels and methylation analysis did not support the hypothesis.Construction of a 1.2-Mb PAC contig (physical and transcription map) : To confirm an imprinted gene cluster on 7q32, such a contig between D7S530 wAD7S649 including MEST was constructed. It contains 70 novel STSs, 9 novel genes, and 6 known genes.Identification of imprinted genes at 7q32 : Among the genes mapped at the contig, the gene^ to be or not to be imprinted included MEST, COPG2, COPG2TT1 (CfTl), KIAA0265, CPA3, CPA1, mdTSGA14. Both MEST and COPG2IT1 are paternally expressed, while CPA3 is maternally expressed Although COPG2 was thought to be paternally expressed, it is actually biallelically expressed. However, a novel EST (COPG2IT1), the antisense transcript from COPG2-intron 20, showed paternally monoallelic expression in fetal tissues. CPA3 showed partially imprinted in the fetal heart, kidney and lung, and the adult prostate, whereas it loses imprinting partially or completely in lymphoblastoid cells. The findings that COPG2, KIAA 0265, CPA 1 and TSGA14 all showed biallelic expression did not support that their imprinting. These findings, especially the absence of imprinting of COPG2 and TSGA14 which are located nearby MEST suggest that the 7q32 region is not strictly controlled as an imprinting domain but controlled by independent imprinting signals.