Auditory Neurogenetics

描述(申请人提供)：听力损失是衰弱和永久性的，影响66%的70岁以上人口(Cruickshanks等人，AmJ·流行病学，1998)，造成人际隔离，并对经济产生重大影响。 在之前的资助期间，我们使用位置克隆技术分别在小鼠突变体的Deafwaddler和颤动中识别Atp2b2和Spnb4的突变(Street EA，1998；Parkinson EA，2001)。对于每个基因座，我们确定了具有不同程度功能损害的多个等位基因。对于deafwaddler来说，Dfw等位基因是功能降低到30%(Penheiter EA)的低晶型，而Dfw 2J和dfvv 3J是明显的零等位基因，移码突变不产生可检测到的蛋白质。我们已经发现，所有等位基因的纯合子突变都是聋人(Konrad-Martin，2001；McCullough和Tempel，提交)。进一步的研究表明，在纯合子缺失小鼠(dfw2J/dfw 2J)中，内淋巴钙浓度从对照组的23mU/M下降到6mU/M(Wood等人，2004年)。内源性钙的这种显著下降可能与深度耳聋、耳锥的退化和丧失(Fonseca-Burke等人，在Prep.中)以及纯合子零Deafwaddler等位基因中的毛细胞丢失(Pujol等人，2001)有关。在杂合子中，没有发现毛细胞丢失，但在高频下会发生听力损失(Konrad-Martin，2001；McCullough和Tempel，提交)。 这些数据表明，钙在内耳中受到严格调控，PMCA2(Atp2b2基因的蛋白质产物)在维持钙平衡方面起着关键作用。在这里，我们建议通过检测其在Atp2b2表达逐渐降低的小鼠的年龄相关性听力损失(AHL)和噪声性听力损失(NIHL)中的作用来扩展我们对Deafwaddler的研究。为了建立一个比较人和老鼠的理论基础，我们将检查PMCA2在人类颞骨中的分布，并询问携带ATP2B2基因缺失的患者是否出现听力损失。为了寻找预防听力损失的药物策略，我们将研究Atp2b2基因调控的分子基础，并询问提高Atp2b2的表达水平是否可以预防小鼠AHL并保护它们免受NIHL的影响。

DESCRIPTION (provided by applicant): Hearing loss is debilitating and permanent, affecting < 66% of the population over age 70 (Cruickshanks et al., Am. J. Epidemiol., 1998), causing interpersonal isolation and having significant financial impact. During the previous funding period, we used positional cloning techniques to identify mutations in Atp2b2 and Spnb4 in the mouse mutant's deafwaddler and quivering, respectively (Street ea, 1998; Parkinson ea, 2001). For each locus we identified multiple alleles with different degrees of functional impairment. For deafwaddler, the dfw allele is a hypomorph with function reduced to 30% (Penheiter ea) while dfw 2J and dfvv 3J are apparent null alleles with frameshift mutations yielding no detectable protein. We have found that homozygous mutants of all alleles are deaf (Konrad-Martin, 2001 ; Mccullough and Tempel, submitted). Further studies have shown that in homozygous null mice (dfw2J/dfw 2J) endolymphatic calcium concentration drops from 23 mu/M in control to 6 mu/M (Wood et al., 2004). This significant drop in endolyphatic calcium may be causally related to profound deafness, to the degeneration and loss of otoconia (Fonseca-Burke et al., in prep.), as well as to hair cell loss (Pujol et al., 2001) in homozygous null deafwaddler alleles. In heterozygotes no hair cell loss is seen yet hearing loss occurs at high frequencies (Konrad-Martin, 2001; McCullough and Tempel, submitted). These data suggest that calcium is tightly regulated in the inner ear and that PMCA2 (the protein product of the Atp2b2 locus) is a critical player in maintaining calcium balance. Here we propose to extend our studies on deafwaddler by examining its contribution to age-related hearing loss (AHL) and noise-induced hearing loss (NIHL) in mice with graded reductions in Atp2b2 expression. To establish a rationale for comparing man with mouse, we will examine the distribution of PMCA2 in human temporal bone and ask whether patients carrying a deletion of the ATP2B2 locus show hearing loss. Toward identifying pharmacological strategies for preventing hearing loss, we will examine the molecular basis of Atp2b2 gene regulation and ask whether increased levels of expression of Atp2b2 can prevent AHL in mice and protect them from NIHL.