Factor V Leiden mutation (R506Q) and the risk of advanced retinopathy of prematurity.

The coagulation factor V Leiden mutation was reported to be a significant (10.7%) risk factor for pre-term deliveries. It is also well known that a portion (10%) of very low birth weight premature babies develop advanced retinopathy of prematurity (ROP) which is a leading cause of blindness in children. However, the relationship between the Leiden mutation and development of advanced ROP is not known. In order to understand this relationship as well as genetic contribution to ROP, in this study, we have analyzed 100 pre-term infants with advanced ROP (stage 4B/5), 20 term babies with a clinically similar disease called familial exudative vitreoretinopathy (FEVR) and 16 normal babies from four different ethnic backgrounds. Our extensive analysis has identified a heterozygous Leiden mutation in four patients (4%) with advanced ROP and in one patient (5%) with sporadic FEVR. DNA sequence analysis has further confirmed this base change as well as heterozygosity. However, the frequency observed in the patients analyzed in our study is lower than reported frequency in the general population (5.4%). Therefore, statistically factor V mutation on its own is not a major risk factor for the above two disorders. However, it may be associated with other additive factors as might be expected for a complex genetic trait.

Connexin 40 expression in bovine and rat retinas.

Retinal neurons are extensively coupled through gap junction intercellular channels, but few connexin subtypes have been identified in mammalian retinal neurons. Based on previous findings that retinal gap junctional coupling is modulated by both dopamine and nitric oxide, presumably through connexin phosphorylation, we examined whether the connexin phosphoprotein subtype, connexin 40 (Cx40), was expressed in mammalian retinas. Immunostaining of rat and bovine retinas using Cx40-specific antibodies from two independent sources showed punctate staining between cells in the outer nuclear layer (ONL) and a sublayer of cells within the inner nuclear layer (INL). In addition, sparse punctate staining was detected in the ganglion cell/axon fiber layers (GCL/AFL). No punctate staining was observed in the outer (OS) or inner segment (IS) layers, and rarely in the outer plexiform layer (OPL) or inner plexiform layer (IPL). Double immunostaining of bovine retinas with antibodies to G(o), which stains bipolar cells, and to Cx40, showed little overlap, suggesting these bipolar cells do not express Cx40. Western blot analysis of alkaline-extracted bovine retinal membranes revealed Cx40 immunopositive bands of about 40 kD (monomer) and 80 kD (dimer). In both locations (monomer and dimer), the bands appeared as doublets, and their immunoreactivity was abolished when the antibody was pre-adsorbed with immunogenic Cx40 peptide. The doublet at 40 kD co-migrated with an immunopositive doublet present in heart membranes. Treatment with alkaline phosphatase altered the banding pattern of Cx40. The results suggest that the connexin phosphoprotein subtype, Cx40, is expressed within the neural layers of the mammalian retina.