Sibs diagnosed prenatally with situs inversus totalis, renal and pancreatic dysplasia, and cysts: a new syndrome?

The zebrafish orthologue of the dyslexia candidate gene DYX1C1 is essential for cilia growth and function

DYX1C1, a susceptibility gene for dyslexia, encodes a tetratricopeptide repeat domain containing protein that has been implicated in neuronal migration in rodent models. The developmental role of this gene remains unexplored. To understand the biological function(s) of zebrafish dyx1c1 during embryonic development, we cloned the zebrafish dyx1c1 and used morpholino-based knockdown strategy. Quantitative real-time PCR analysis revealed the presence of dyx1c1 transcripts in embryos, early larval stages and in a wide range of adult tissues. Using mRNA in situ hybridization, we show here that dyx1c1 is expressed in many ciliated tissues in zebrafish. Inhibition of dyx1c1 produced pleiotropic phenotypes characteristically associated with cilia defects such as body curvature, hydrocephalus, situs inversus and kidney cysts. We also demonstrate that in dyx1c1 morphants, cilia length is reduced in several organs including Kupffer’s vesicle, pronephros, spinal canal and olfactory placode. Furthermore, electron microscopic analysis of cilia in dyx1c1 morphants revealed loss of both outer (ODA) and inner dynein arms (IDA) that have been shown to be required for cilia motility. Considering all these results, we propose an essential role for dyx1c1 in cilia growth and function.

Autosomal dominant polycystic kidney disease with situs inversus

Situs inversus totalis and autosomal dominant polycystic kidney disease (ADPKD) occur with an incidence of 1/10,000 in the general population and 1 in 1000 live births, respectively. Association of the two conditions is rare and there are few pediatric case reports. Association of situs inversus totalis and autosomal recessive polycystic kidney disease has also been reported. Recent studies have revealed ciliary dysfunction as a cause of both conditions.

New syndrome?: Three sibs diagnosed prenatally with situs inversus totalis, renal and pancreatic dysplasia, and cysts

Recently we described a previously apparently undescribed autosomal recessive syndrome in two sib fetuses with situs inversus totalis, cystic dysplastic kidneys and pancreas, bowing of the lower limbs and clavicles, severe intrauterine growth retardation, and oligohydramnios. This syndrome differs from that of Ivemark and related syndromes due to lack of liver involvement. After these two sibs, this consanguineous family had a third child and an early prenatal diagnosis of pancreatic and dysplastic renal cysts was made in the 19.5-week-old fetus. The last case supports the genetic hypothesis.