Eye defects in receptor protein‐tyrosine phosphatase α knock‐down zebrafish

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Abstract
Receptor protein‐tyrosine phosphatase alpha (RPTPα) is highly expressed in the developing retina of different species, but little is known about its function there. Here, we report that injection of antisense morpholinos in zebrafish embryos reduced RPTPα expression to almost nondetectable levels up to 3 days postfertilization (dpf). RPTPα was detectable again from 4 dpf onward. RPTPα knock‐down resulted in smaller eyes. Examination of sections of the retina at different developmental stages demonstrated that already at 28 hours postfertilization (hpf) fewer cells were present in the retina of RPTPα‐morpholino–injected embryos. At 3 dpf, the layered organization of the retina was absent. In addition, the morphology and labeling with an axon specific antibody, acetylated tubulin, demonstrated that most cells appeared to be undifferentiated. Strikingly, at 5 dpf the lamination of the retina was partially restored, concomitant with re‐expression of RPTPα protein. Although cells in the retina were now differentiated, the layering of the retina remained disrupted and significant gaps were observed in the amacrine cell layer. Therefore, knock‐down of RPTPα protein provides evidence that RPTPα is essential for normal retinal development.