Orr Andrew, Dubé Marie-Pierre, Zenteno Juan C, Jiang Haiyan, Asselin Geraldine, Evans Susan C, Caqueret Aurore, Lakosha Hesham, Letourneau Louis, Marcadier Julien, Matsuoka Makoto, Macgillivray Christine, Nightingale Mathew, Papillon-Cavanagh Simon, Perry Scott, Provost Sylvie, Ludman Mark, Guernsey Duane L, Samuels Mark E
Department of Ophthalmology and Visual Sciences, Dalhousie University, Halifax, Nova Scotia, Canada.
Mol Vis. 2011;17:1850-61. Epub 2011 Jul 12.
Nanophthalmos is a rare genetic ocular disorder in which the eyes of affected individuals are abnormally small. Patients suffer from severe hyperopia as a result of their markedly reduced axial lengths, but otherwise are capable of seeing well unlike other more general forms of microphthalmia. To date one gene for nanophthalmos has been identified, encoding the membrane-type frizzled related protein MFRP. Identification of additional genes for nanophthalmos will improve our understanding of normal developmental regulation of eye growth.
We ascertained a cohort of families from eastern Canada and Mexico with familial nanophthalmos. We performed high density microsatellite and high density single nucleotide polymorphism (SNP) genotyping to identify potential chromosomal regions of linkage. We sequenced coding regions of genes in the linked interval by traditional PCR-based Sanger capillary electrophoresis methods. We cloned and sequenced a novel cDNA from a putative causal gene to verify gene structure.
We identified a linked locus on chromosome 2q37 with a peak logarithm (base 10) of odds (LOD) score of 4.7. Sequencing of coding exons of all genes in the region identified multiple segregating variants in one gene, recently annotated as serine protease gene (PRSS56), coding for a predicted trypsin serine protease-like protein. One of our families was homozygous for a predicted pathogenic missense mutation, one family was compound heterozygous for two predicted pathogenic missense mutations, and one family was compound heterozygous for a predicted pathogenic missense mutation plus a frameshift leading to obligatory truncation of the predicted protein. The PRSS56 gene structure in public databases is based on a virtual transcript assembled from overlapping incomplete cDNA clones; we have now validated the structure of a full-length transcript from embryonic mouse brain RNA.
PRSS56 is a good candidate for the causal gene for nanophthalmos in our families.
小眼球症是一种罕见的遗传性眼部疾病，患者的眼睛异常小。由于眼轴长度显著缩短，患者患有严重远视，但与其他更常见的小眼症形式不同，他们在其他方面视力良好。迄今为止，已鉴定出一个与小眼球症相关的基因，该基因编码膜型卷曲相关蛋白MFRP。鉴定出更多与小眼球症相关的基因将有助于我们更好地理解眼睛生长的正常发育调控机制。
我们确定了来自加拿大东部和墨西哥的患有家族性小眼球症的家系群体。我们进行了高密度微卫星和高密度单核苷酸多态性（SNP）基因分型，以确定潜在的连锁染色体区域。我们通过基于传统PCR的桑格毛细管电泳方法对连锁区间内基因的编码区进行测序。我们从一个假定的致病基因中克隆并测序了一个新的cDNA，以验证基因结构。
我们在2号染色体q37上鉴定出一个连锁位点，对数优势（LOD）分数峰值为4.7。对该区域所有基因的编码外显子进行测序，发现一个基因中有多个分离变异，该基因最近被注释为丝氨酸蛋白酶基因（PRSS56），编码一种预测的胰蛋白酶丝氨酸蛋白酶样蛋白。我们的一个家系对一个预测的致病错义突变是纯合的，一个家系对两个预测的致病错义突变是复合杂合的，还有一个家系对一个预测的致病错义突变加上一个导致预测蛋白必然截短的移码突变是复合杂合的。公共数据库中的PRSS56基因结构基于从重叠的不完整cDNA克隆组装而成的虚拟转录本；我们现在已经验证了来自胚胎小鼠脑RNA的全长转录本的结构。
PRSS56是我们研究的家系中小眼球症致病基因的一个良好候选基因。
