Altered Self-Erythrocyte Recognition and Destruction in an Inbred Line of Tilapia (Oreochromis aureus)

Abstract

Carboxyfluorescein diacetate (cFDA)-stained autologous and syngeneic tilapia (Oreochromis aureus) erythrocytes are recognized by effector peripheral blood leukocytes and lysed after a short culture period of 4 h. The hemolysis level was evaluated by measuring the fluorescence of the released cFDA. The degree of lysis of stained target erythrocytes of 60 individuals revealed a trimodal distribution statistically stratified into three groups of low (LR), intermediate (IR), and high (HR) responders. Depletion of the majority of phagocytes from leukocytes lowered the lysis level of HR to that of LR. A highly significant increase of LR cytotoxicity was obtained after the addition of conditioned medium from HR but only in the presence of phagocytes. Genetic analysis of offspring from four crosses (IR × HR, IR × LR, HR × LR, and LR × LR) revealed a quantitative trait locus (QTL) segregating for the level of response linked to markers UNH207 and UNH231 on linkage group 6 of tilapia. Based on segregation analysis of 58 gynogenetic BIU-1 offspring, the distances from the centromere were estimated as 21.5, 11.5, and 9.0 cM for UNH207, UNH231, and the QTL, respectively. It is suggested that 1) self-target recognition and destruction requires both cFDA-altered self-erythrocyte membrane and membrane structures normally present in autologous, syngeneic, and xenogeneic targets; 2) natural cytotoxic cells and/or macrophages are involved in erythrocyte lysis; and 3) the lysis level is codominantly inherited by a QTL segregating on tilapia linkage group 6.

A deleterious effect associated with UNH159 is attenuated in twin embryos of an inbred line of blue tilapia Oreochromis aureus

“…Forty‐four normal full‐sibs of the same developmental stage were also fixed in alcohol for comparison in order to examine the possible association between twinning incidences and specific markers. Five of the seven microsatellite markers (UNH101, 148, 159, 187 and 190), which were previously shown to amplify polymorphic products in BIU‐1 inbred line (Shirak et al , 2006) were polymorphic in both parents and, therefore, were used for the twinning analysis in this study. In order to verify the difference in genotypic segregation for UNH159, additional 84 samples of normal full‐sibs were genotyped with this marker.…”

“…Palti et al (2002) reported genetic markers that were associated with deleterious effects in a meiogynogenetic tilapia line (BIU‐1). In this gynogenetic line, the number of polymorphic microsatellite markers gradually decreased from 76 in the original stock to 20, 11 and seven in the third, fourth and fifth generations, respectively (Palti et al , 2002; Shirak et al , 2006). By examining dozens of morphological and immunological traits for variability in this line, high uniformity was observed.…”

“…By examining dozens of morphological and immunological traits for variability in this line, high uniformity was observed. The trait of cytotoxic reaction of blood leucocytes, however, was still variable in the fifth generation and associated with two of the microsatellite markers (Shirak et al , 2006). Preliminary observations indicted that twinning rate also remained variable.…”

Microsatellite Support for Active Inbreeding in a Cichlid Fish

“…Based on a linkage map of 525 microsatellite loci available from Oreochromis niloticus [45], a subset of 169 microsatellite loci were selected. These microsatellites are all dinucleotide repeats of the type (CA) n and have been successfully cross-species amplified in other cichlid studies [46], [47]. Assuming that the location of the loci on the chromosomes is similar in Pelvicachromis and O. niloticus , loci were chosen from different chromosomes in order to assure representative coverage of the whole genome.…”