MOLECULAR GENETICS OF CD TOXICITY

该项目的长期目标是识别和表征导致镉(Cd++)反应个体间差异的基因(S)。镉是一种广泛存在的环境污染物，被归类为国际癌症研究机构的“第一类”人类致癌物质。镉还会导致严重的肾脏毒性和心血管疾病。人类对镉毒性的易感性存在遗传差异，而近亲交配的小鼠则有明确的遗传数据。1973年，在小鼠染色体(Chr)3上发现了一个与镉引起的睾丸损伤有关的隐性基因，命名为CDM。借助小鼠基因组计划的最新进展和对半定量组织学参数的研究，我们现在已经证实了1973年的原始数据，并利用多态微卫星标记，将CDM基因的染色体位置从24厘米(Cm)精确到0.64 cM(估计40-80个基因)。我们利用C57BL/6J(B6，抗性)和DBA/2J(D2，敏感)近交系小鼠产生的重组近交系，确定了CDM基因在微卫星标记D3Mit110和D3Mit255之间的定位。有强有力的证据表明，Cd++通过引起特定细胞类型的氧化应激来发挥其毒性作用，这可能导致细胞大分子的共价修饰或细胞周期中断-导致细胞分裂增强、细胞凋亡或生长停滞。我们将定位和鉴定CDM基因，我们的假设是CDM基因编码一种特定细胞类型的蛋白质，该蛋白质在镉诱导的细胞氧化还原动态平衡的破坏中发挥重要作用。因此，我们建议[1]通过识别B6和D2小鼠之间的单核苷酸多态(SNPs)，然后确定这些新标记在BXD14/Ty小鼠中的基因型，来缩小Chr3上包含CDM基因的区域；[2]测序包含CDM基因区域的部分序列，并在耐Cd++的B6小鼠背景上识别将赋予睾丸对Cd++敏感性的BAC克隆；以及[3]从特殊的AIM 1号和2号产生的基因组序列中识别CDM基因。尽管对多种重金属的毒性是众所周知的，但分子机制尚未在人类或实验哺乳动物中揭示。这些研究将通过首次识别和表征导致镉诱导毒性易感性的主要基因来加深我们对重金属毒性的理解。

The long-term goal of this project is to identify and characterize the gene(s) responsible for interindividual differences in response to cadmium (Cd++). Cadmium is a widespread environmental pollutant and is classifed as an IARC "Category I" human carcinogen. Cadmium can also cause severe renal toxicity and cardiovascular disease. Genetic differences in susceptibility to cadmium toxicity have been suggested in humans, whereas in inbred mice there are unequivocal genetic data. Resistance to cadmium-induced testicular damage was reported in 1973 to be associated with a single recessive gene, named Cdm, found on mouse chromosome (Chr) 3. With the help of recent advances in the Mouse Genome Project and studying semiquantitative histological parameters, we have now corroborated the original 1973 data and, using polymorphic microsatellite markers, have refined the chromosomal location of the Cdm gene from more than 24 centiMorgans (cM) to 0.64 cM (estimated 40-80 genes). We have used recombinant inbred lines generated from C57BL/6J (B6, resistant) and DBA/2J (D2, sensitive) inbred mice to determine that the Cdm gene maps between microsatellite markers D3Mit110 and D3Mit255. There is strong evidence that Cd++ exerts its toxic effects by causing cell type-specific oxidative stress which can result in the covalent modification of cellular macromolecules or disruption of the cell cycle-leading to enhanced cell division, apoptosis or growth arrest. We will locate and identify the Cdm gene, and our hypothesis is that the Cdm gene encodes a protein in specific cell types that plays an important role in cadmium-induced disruption of cellular redox homeostasis. Thus, we propose to [1] narrow the Cdm-gene-containing region on Chr 3, by identifying single nucleotide polymorphisms (SNPs) between B6 and D2 mice, and then determining the genotype of these new markers in the BXD14/Ty mouse ; [2] sequence portions of the Cdm-gene- containing region and identify a BAC clone that will confer testicular sensitivity to Cd++ on a resistant B6 mouse background; and [3] identify the Cdm gene from the genomic sequences produced in Spec.Aims number 1 and number 2. Although toxicity to numerous heavy metals is well known, molecular mechanisms have yet to be uncovered - in humans or laboratory mammals. These studies will enhance our understanding of heavy metal toxicity by identifying and characterizing, for the first time, a major gene responsible for susceptibility to cadmium-induced toxicity.