title: Genetic and immunohistochemical analysis of HSPA5 in mouse and human retinas.
abstract: Photoreceptor degenerative diseases are among the leading causes of vision loss. Although the causative genetic mutations are often known, mechanisms leading to photoreceptor degeneration remain poorly defined. We have previously demonstrated that the photoreceptor membrane-associated protein XAP-1 antigen is a product of theHSPA5gene. In this study, we used systems genetic methods, statistical modeling, and immunostaining to identify and analyze candidate genes that modulate Hspa5 expression in the retina.
  
  
  
  Quantitative trait locus (QTL) mapping was used to map the genomic region that regulatesHspa5in the cross between C57BL/6J X DBA/2J mice (BXD) genetic reference panel. The stepwise refinement of candidate genes was based on expression QTL mapping, gene expression correlation analyses (direct and partial), and analysis of regional sequence variants. The subcellular localization of candidate proteins and HSPA5 in mouse and human retinas was evaluated by immunohistochemistry. Differences in the localization of extracellular HSPA5 were assessed between healthy human donor and atrophic age-related macular degeneration (AMD) donor eyes.
  
  
  
  In the eyes of healthy mice, extracellular HSPA5 was confined to the area around the cone photoreceptor outer segments. Mapping variation inHspa5mRNA expression levels in the retina revealed a statistically significanttrans-acting expression QTL (eQTL) on Chromosome 2 (Chr 2) and a suggestive locus on Chr 15.Sulf2on Chr 2 was the strongest candidate gene based on partial correlation analysis, Pearson correlation withHspa5, expression levels in the retina, a missense variant in exon 14, and its reported function in the extracellular matrix and interphotoreceptor matrix. SULF2 is localized to the rod and cone photoreceptors in both human and mouse retinas. In human retinas with no pathology, extracellular HSPA5 was localized around many cones within the macular area. In contrast, fewer HSPA5-immunopositive cones were observed in the retinas from AMD donors.
  
  
  
  We identifiedSulf2as a candidate gene modulating theHspa5expression in the retina. The preferential loss of HSPA5 in the interphotoreceptor matrix around cone photoreceptors in atrophic AMD retinas opens up new avenues for exploring the changes in interphotoreceptor matrix (IPM) that are associated with macular disease.
authors.affiliation: Department of Ophthalmology, Hamilton Eye Institute, The University of Tennessee Health Science Center, Memphis, TN; Department of Anatomy and Neurobiology, The University of Tennessee Health Science Center, Memphis, TN.
authors.forename: Sumana R
authors.initials: SR
authors.lastname: Chintalapudi
authors.affiliation: Department of Ophthalmology, Hamilton Eye Institute, The University of Tennessee Health Science Center, Memphis, TN.
authors.forename: XiaoFei
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Ophthalmology, Hamilton Eye Institute, The University of Tennessee Health Science Center, Memphis, TN; Department of Ophthalmology, the Second Xiangya Hospital, Central South University, Changsha, Hunan, China.
authors.forename: Huiling
authors.initials: H
authors.lastname: Li
authors.affiliation: Department of Ophthalmology, Hamilton Eye Institute, The University of Tennessee Health Science Center, Memphis, TN.
authors.forename: Yin H Chan
authors.initials: YH
authors.lastname: Lau
authors.affiliation: Department of Anatomy and Neurobiology, The University of Tennessee Health Science Center, Memphis, TN; Department of Genetics, Genomics and Informatics, The University of Tennessee Health Science Center, Memphis, TN.
authors.forename: Robert W
authors.initials: RW
authors.lastname: Williams
authors.affiliation: Department of Ophthalmology, Hamilton Eye Institute, The University of Tennessee Health Science Center, Memphis, TN; Department of Anatomy and Neurobiology, The University of Tennessee Health Science Center, Memphis, TN; Department of Pharmaceutical Sciences, The University of Tennessee Health Science Center, Memphis, TN.
authors.forename: Monica M
authors.initials: MM
authors.lastname: Jablonski
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D019295:Computational Biology; D000091342:Endoplasmic Reticulum Chaperone BiP; D005260:Female; D005786:Gene Expression Regulation; D056726:Genetic Association Studies; D006360:Heat-Shock Proteins / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D012160:Retina / Q000166:cytology / Q000378:metabolism*; D013429:Sulfatases / Q000235:genetics / Q000378:metabolism; D014019:Tissue Donors
chemical_list: D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; C000717248:Hspa5 protein, mouse; C514911:Sulf2 protein, mouse; D013429:Sulfatases