Up-regulation of CD81 (target of the antiproliferative antibody; TAPA) by reactive microglia and astrocytes after spinal cord injury int he rat

We examined the expression of CD81 (also known as TAPA, or target of the antiproliferative antibody) after traumatic spinal cord injury in the rat. CD81, a member of the tetraspanin family of proteins, is thought to be involved in reactive gliosis. This is based on the antiproliferative and antiadhesive effects of antibodies against CD81 on cultured astrocytes, as well as its up-regulation after penetrating brain injury. CD81 expression following dorsal hemisection of the spinal cord was determined immunohistochemically at time points ranging from 1 day to 2 months postlesion (p.l.). In the unlesioned cord a low background level of CD81 was observed, with the exception of the ependyma of the central canal and the pia mater, which were strongly CD81-positive. One day p.l., CD81 was diffusely up-regulated in the spinal cord parenchyma surrounding the lesion site. From 3 days onward, intensely CD81-positive round cells entered the lesion site, completely filling it by 7 days p.l. Staining with the microglial markers OX-42 and Iba1 revealed that these cells were reactive microglia/macrophages. At this time, no significant CD81 expression by GFAP-positive reactive astrocytes was noted. From the second week onward, CD81 was gradually down-regulated; i.e., its spatial distribution became more restricted. The CD81-positive microglia/macrophages disappeared from the lesion site, leaving behind large cavities. After 2 months, astrocytes that formed the wall of these cavities were strongly CD81-positive. In addition, CD81 was present on reactive astrocytes in the dorsal funiculus distal from the lesion in degenerated white matter tracts. In conclusion, the spatiotemporal expression pattern of CD81 by reactive microglia and astrocytes indicates that CD81 is involved in the glial response to spinal cord injury

Targeting the tetraspanin CD81 blocks monocyte transmigration and ameliorates EAE

Leukocyte infiltration is a key step in the development of demyelinating lesions in multiple sclerosis (MS), and molecules mediating leukocyte-endothelial interactions represent prime candidates for the development of therapeutic strategies. Here we studied the effects of blocking the integrin-associated tetraspanin CD81 in in vitro and in vivo models for MS. In an in vitro setting mAb against CD81 significantly reduced monocyte transmigration across brain endothelial cell monolayers, both in rodent and human models. Interestingly, leukocyte as well as endothelial CD81 was involved in this inhibitory effect. To assess their therapeutic potential, CD81 mAb were administered to mice suffering from experimental autoimmune encephalomyelitis (EAE). We found that Eat2, but not 2F7 mAb directed against mouse CD81 significantly reduced the development of neurological symptoms of EAE when using a preventive approach. Concomitantly, Eat2 treated animals showed reduced inflammation in the spinal cord. We conclude that CD81 represents a potential therapeutic target to interfere with leukocyte infiltration and ameliorate inflammatory neurological damage in MS. © 2008 Elsevier Inc. All rights reserved

Genomic locus modulating corneal thickness in the mouse identifies POU6F2 as a potential risk of developing glaucoma

Central corneal thickness (CCT) is one of the most heritable ocular traits and it is also a phenotypic risk factor for primary open angle glaucoma (POAG). The present study uses the BXD Recombinant Inbred (RI) strains to identify novel quantitative trait loci (QTLs) modulating CCT in the mouse with the potential of identifying a molecular link between CCT and risk of developing POAG. The BXD RI strain set was used to define mammalian genomic loci modulating CCT, with a total of 818 corneas measured from 61 BXD RI strains (between 60–100 days of age). The mice were anesthetized and the eyes were positioned in front of the lens of the Phoenix Micron IV Image-Guided OCT system or the Bioptigen OCT system. CCT data for each strain was averaged and used to QTLs modulating this phenotype using the bioinformatics tools on GeneNetwork (www.genenetwork.org). The candidate genes and genomic loci identified in the mouse were then directly compared with the summary data from a human POAG genome wide association study (NEIGHBORHOOD) to determine if any genomic elements modulating mouse CCT are also risk factors for POAG.This analysis revealed one significant QTL on Chr 13 and a suggestive QTL on Chr 7. The significant locus on Chr 13 (13 to 19 Mb) was examined further to define candidate genes modulating this eye phenotype. For the Chr 13 QTL in the mouse, only one gene in the region (Pou6f2) contained nonsynonymous SNPs. Of these five nonsynonymous SNPs in Pou6f2, two resulted in changes in the amino acid proline which could result in altered secondary structure affecting protein function. The 7 Mb region under the mouse Chr 13 peak distributes over 2 chromosomes in the human: Chr 1 and Chr 7. These genomic loci were examined in the NEIGHBORHOOD database to determine if they are potential risk factors for human glaucoma identified using meta-data from human GWAS. The top 50 hits all resided within one gene (POU6F2), with the highest significance level of p = 10−6 for SNP rs76319873. POU6F2 is found in retinal ganglion cells and in corneal limbal stem cells. To test the effect of POU6F2 on CCT we examined the corneas of a Pou6f2-null mice and the corneas were thinner than those of wild-type littermates. In addition, these POU6F2 RGCs die early in the DBA/ 2J model of glaucoma than most RGCs. Using a mouse genetic reference panel, we identified a transcription factor, Pou6f2, that modulates CCT in the mouse. POU6F2 is also found in a subset of retinal ganglion cells an