Prenatal description of retinal coloboma.

Retinal coloboma is a rare condition which is difficult to diagnose in foetuses. It can cause blindness. It can be isolated or associated with other malformations in various syndromes. Our objective is to describe the different prenatal ultrasound findings and management of coloboma. We describe a case of prenatal ultrasound diagnosis of retinal coloboma at 27.5 weeks of gestation. Our case adds to the 8 previously reported in the prenatal ultrasound literature, which together illustrate that microphthalmia is the main associated sign, present in 66.6% (6/9) of cases followed by retro-orbital cysts (44.4%) (4/9). These two ultrasound findings should alert us to a close examination of the eye to look for a posterior retinal cleft, the main direct sign of a chorioretinal coloboma.

Abrogation of Stem Loop Binding Protein (Slbp) function leads to a failure of cells to transition from proliferation to differentiation, retinal coloboma and midline axon guidance deficits.

Through forward genetic screening for mutations affecting visual system development, we identified prominent coloboma and cell-autonomous retinal neuron differentiation, lamination and retinal axon projection defects in eisspalte (ele) mutant zebrafish. Additional axonal deficits were present, most notably at midline axon commissures. Genetic mapping and cloning of the ele mutation showed that the affected gene is slbp, which encodes a conserved RNA stem-loop binding protein involved in replication dependent histone mRNA metabolism. Cells throughout the central nervous system remained in the cell cycle in ele mutant embryos at stages when, and locations where, post-mitotic cells have differentiated in wild-type siblings. Indeed, RNAseq analysis showed down-regulation of many genes associated with neuronal differentiation. This was coincident with changes in the levels and spatial localisation of expression of various genes implicated, for instance, in axon guidance, that likely underlie specific ele phenotypes. These results suggest that many of the cell and tissue specific phenotypes in ele mutant embryos are secondary to altered expression of modules of developmental regulatory genes that characterise, or promote transitions in, cell state and require the correct function of Slbp-dependent histone and chromatin regulatory genes.

Retinal cysts in the eye of the Asian musk shrew, Suncus murinus, (Mammalia, Insectivora).

The development of retinal cysts in the eye primordia of Suncus murinus embryos was studied. Retinal infoldings were first identified in the 17.5-day-old embryo (crown rump length--CRL = 6.3 mm). At this time, the apex of the developing retinal fold could be identified attached to the lens. The pigmented epithelium did not take part in the formation of the cyst. The retinal fold closed, to form a cyst, by day 23 of embryonic development (CRL = 14.0 mm). The newly formed retinal cyst remained continuous with the retina and extended toward the lens where it attached to the lens epithelium. Retinal cysts had an oval, bilaterally symmetrical shape and a narrow lumen, which, lined by the internal limiting membrane, occasionally contained cellular debris. The dimensions of the cysts were usually 100 to 150 microns (diameter) by 200 to 250 microns (length). Retinal cysts appeared in 45 per cent of the embryos examined.

Association between cilioretinal arteries and juxtapapillary scars.

We examined the relationship of cilioretinal arteries (CRAs) to juxtapapillary chorioretinal scars, along with the developmental significance of the latter in relation to CRA formation. Both eyes of 360 patients were studied. Sixty-eight (18.9%) of these patients had a CRA in at least one eye, 13 of these 68 (19.1%) had one in both. The CRAs were distributed equally between right and left eyes. Two hundred eight patients (57.8%) had a scar in at least one eye; 157 of these (75.5%) had one in both. The presence of a CRA was significantly associated with the presence of a scar. Since both are common developmental variations, this correlation points to a common embryologic formation mechanism.

Use of a culture system to identify possible causes of abnormal retinal development.

The aim of this study was to apply a recently developed cell culture system to the problem of identifying possible etiologies of altered retinal maturation. Using techniques of electrophysiology and neuropharmacology, it was possible to monitor the release of acetylcholine at synapses formed by cultured retinal neurons derived from the fetal rat. The major finding of this study was that the functional development of cholinergic retinal neurons of the fetus could be altered if the mother rat had been injected with a synthetic glucocorticoid hormone or stressed by cold exposure during a critical period in pregnancy. Thus, the maturation of at least certain fetal retinal neurons appears to be influenced by factors affecting the mother. The culture system described here provides a potentially useful approach to the identification and investigation of possible causes of abnormalities in the functional development of the mammalian retina.

Autosomal dominant preretinal vascular loops.

Preretinal vascular loops are a congenital malformation usually occurring in otherwise normal fundi. These anomalies consist of vessels, most commonly arteries, that spiral into the vitreous and return to the otherwise normal retinal vascular system. The authors present two members of a family with preretinal vascular loops and two members with other vascular anomalies. The inheritance pattern in this group is autosomal dominant.