Defects in the rhodopsin kinase gene in the Oguchi form of stationary night blindness.

Oguchi disease is a recessively inherited form of stationary night blindness due to malfunction of the rod photoreceptor mechanism. Patients with this disease show a distinctive golden-brown colour of the fundus that occurs as the retina adapts to light, called the Mizuo phenomenon. Recently a defect in arrestin, a member of the rod phototransduction pathway, was found to cause this disease in some Japanese patients. As rhodopsin kinase works with arrestin in shutting off rhodopsin after it has been activated by a photon of light, it is reasonable to propose that some cases of Oguchi disease might be caused by defects in rhodopsin kinase. This report describes an analysis of the arrestin and rhodopsin kinase genes in three unrelated cases of Oguchi disease. No defects in arrestin were detected, but all three cases had mutations in the rhodopsin kinase gene. Two cases were found to be homozygous for a deletion encompassing exon 5, predicted to lead to a nonfunctional protein. The third case was a compound heterozygote with two allelic mutations, a missense mutation (Val380Asp) affecting a residue in the catalytic domain, and a frameshift mutation (Ser536(4-bp del)) resulting in truncation of the carboxy terminus. Our results indicate that null mutations in the rhodopsin kinase gene are a cause of Oguchi disease and extend the known genetic heterogeneity in congenital stationary night blindness.

Evaluation of the human arrestin gene in patients with retinitis pigmentosa and stationary night blindness.

PURPOSE: To establish the DNA sequence of the coding regions of the human arrestin locus and to determine whether defects in this sequence are present among patients with retinitis pigmentosa (RP) or types of stationary night blindness in addition to Oguchi disease. METHODS: The human genomic locus encoding arrestin was cloned in bacteriophage and P1 vectors. The sequence of the intron DNA flanking each exon was determined from these clones. Single-strand conformation polymorphism analysis and direct genomic sequencing techniques were used to screen 272 unrelated patients, comprising 177 patients with autosomal dominant RP, 85 with recessive RP, and 10 with stationary night blindness. RESULTS: The arrestin gene is divided into 16 exons ranging in size from 10 bp to 194 bp, with the open reading frame spanning exons 2 through 16. The authors identified several discrepancies between the genomic sequence the authors obtained and the previously published cDNA and genomic sequences. In the set of patients with dominant RP, the authors found one of three heterozygous missense changes (Arg84Cys, Thr125Met, and Val378Ile) in each of four unrelated patients; none of these changes cosegregated with disease in the respective families. In the set of patients with recessive RP, the authors found one of two heterozygous missense changes in each of two unrelated patients with recessive RP (Pro364Leu and Arg384Cys). One of the patients was the offspring of a consanguineous marriage; because the Arg384Cys change in him was heterozygous, it is unlikely to have been the cause of his RP. Cosegregation studies could not be performed on the patient with the Pro364Leu change. The authors confirmed the existence of two previously described polymorphisms (Ile76Val and a multiallelic polymorphism at codon 403), and the authors identified several silent polymorphisms and rare sequence variants. No sequence changes, other than polymorphic changes also found in some patients with RP, were identified in the patients with stationary night blindness. CONCLUSIONS: We found no evidence that mutations in arrestin are a cause of RP or stationary night blindness other than Oguchi disease. According to the genomic sequence obtained, a region in exon 8 that has been postulated to represent the site of interaction between arrestin and rhodopsin is 100% conserved between humans and all other mammals studied to date.

Amniotic membrane surgery.

Human amniotic membrane (AM) is composed of three layers: a single epithelial layer, a thick basement membrane, and an avascular stroma. Amniotic membrane has anti-adhesive properties and is felt to promote epithelialization and decrease inflammation, neovascularization, and fibrosis. Amniotic membrane transplantation (AMT) is currently being used for a continuously widening spectrum of ophthalmic indications. Amniotic membrane transplantation has been shown to be effective in the reconstruction of the corneal surface in the setting of persistent epithelial defects, sterile corneal ulcerations, and partial limbal stem cell (LSC) deficiency states, including those secondary to chemical or thermal burns. Amniotic membrane transplantation also has been used in conjunction with limbal stem cell transplantation (LSCT) both in a concurrent fashion as well as in preparation for LSCT. Amniotic membrane transplantation also has been used in place of conjunctival autografting after pterygium excision and to reconstruct the conjunctival surface after removal of conjunctival lesions. Most recently, ex vivo cultivation and expansion of limbal epithelial cells has been performed utilizing AM as a matrix. However, the superiority of AMT over other treatment modalities in many of these settings needs to be substantiated by controlled clinical trials.

Frequency of somatic and germ-line mosaicism in retinoblastoma: implications for genetic counseling.

Although mosaicism can have important implications for genetic counseling of families with hereditary disorders, information regarding the incidence of mosaicism is available for only a few genetic diseases. Here we describe an evaluation of 156 families with retinoblastoma; the initial oncogenic mutation in the retinoblastoma gene had been identified in these families. In 15 ( approximately 10%) families, we were able to document mosaicism for the initial mutation in the retinoblastoma gene, either in the proband or in one of the proband's parents. The true incidence of mosaicism in this group of 156 families is probably higher than our findings indicate; in some additional families beyond the 15 we identified, mosaicism was likely but could not be proven, because somatic or germ-line DNA from key family members was unavailable. Germ-line DNA from two mosaic fathers was analyzed: in one of these, the mutation was detected in both sperm and leukocyte DNA; in the other, the mutation was detected only in sperm DNA. Our data suggest that mosaicism is more common than is generally appreciated, especially in disorders such as retinoblastoma, in which a high proportion of cases represent new mutations. The possibility of mosaicism should always be considered during the genetic counseling of newly identified families with retinoblastoma. As demonstrated here, genetic tests of germ-line DNA can provide valuable information that is not available through analysis of somatic (leukocyte) DNA.

T lymphocyte T cell-B cell-activating molecule/CD40-L molecules induce normal B cells or chronic lymphocytic leukemia B cells to express CD80 (B7/BB-1) and enhance their costimulatory activity.

Activation-induced cell surface molecules are involved in mediating bidirectional T-B lymphocyte signaling that is important in the induction of T or B lymphocyte effector functions. In this regard, T-BAM/CD40-L is an activation-induced CD4+ T cell surface molecule known to be important in inducing B cell effector functions. This report demonstrates that T-BAM/CD40-L molecules on a Jurkat T cell leukemia subclone (D1.1) or nonlymphoid 293 kidney cell transfectants induce B cells or B-CLL cells to express CD80 (B7/BB-1) in a manner that is specifically inhibited by anti-T-BAM/CD40-L mAb 5C8. Because activation-induced B cell surface molecules, such as CD80, deliver costimulatory signals to T cells that augment T cell proliferation, the functional costimulatory capacity of T-BAM/CD40-L-primed B cells and B-CLL cells was studied. T-BAM/CD40-L-primed B cells or B-CLL cells augment the proliferative responses of allogenic T cells. Furthermore, T-BAM/CD40-L priming is specifically inhibited by mAb 5C8. Together, these studies demonstrate that T-BAM/CD40-L induces CD80 expression on resting B cells or B-CLL cells. Moreover, T-BAM/CD40-L signaling enhances B cell costimulatory capacity. These studies suggest that T-BAM/CD40-L molecules not only induce B cell differentiative processes that result in Ab secretion, but also enable B cells to prime Ag-specific T cells for subsequent clonal expansion.