MOLECULAR GENETICS OF CD TOXICITY

该项目的长期目标是确定和表征负责镉（Cd++）反应的个体间差异的基因。 镉是一种广泛的环境污染物，被IARC列为“I类”人类致癌物。 镉还可导致严重的肾毒性和心血管疾病。 人类对镉毒性的易感性存在遗传差异，而在近交系小鼠中有明确的遗传数据。 1973年，研究人员发现，镉对小鼠睾丸损伤的抵抗力与一个位于小鼠3号染色体上的隐性基因Cdm有关。 借助小鼠基因组计划的最新进展和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，并使用多态性微卫星标记，将Cdm基因的染色体定位从24 cM以上精确到0.64 cM（估计有40-80个基因）。 我们使用C57 BL/6 J（B6，抗性）和DBA/2 J（D2，敏感）近交系小鼠产生的重组近交系，以确定Cdm基因微卫星标记D3 Mit 110和D3 Mit 255之间的地图。 有强有力的证据表明，Cd++通过引起细胞类型特异性氧化应激而发挥其毒性作用，该氧化应激可导致细胞大分子的共价修饰或细胞周期的破坏，从而导致细胞分裂增强、凋亡或生长停滞。 我们将定位并鉴定Cdm基因，我们的假设是Cdm基因编码特定细胞类型中的蛋白质，该蛋白质在镉诱导的细胞氧化还原稳态破坏中起重要作用。 因此，我们建议[1]通过鉴定B6和D2小鼠之间的单核苷酸多态性（SNP），然后确定BXD 14/Ty小鼠中这些新标记的基因型，来缩小Chr 3上含Cdm基因的区域; [2]对含Cdm基因的区域的部分进行测序，并鉴定将在抗性B6小鼠背景下赋予睾丸对Cd++敏感性的BAC克隆;和[3]从在规格1和规格2中产生的基因组序列中鉴定Cdm基因。虽然许多重金属的毒性是众所周知的，但分子机制尚未被发现-在人类或实验室哺乳动物中。 这些研究将提高我们对重金属毒性的理解，通过识别和表征，第一次，一个主要的基因负责镉诱导的毒性易感性。

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.