Clinical utility gene card for: renal coloboma (Papillorenal) syndrome

Inherited Eye Diseases with Retinal Manifestations through the Eyes of Homeobox Genes

Retinal development is under the coordinated control of overlapping networks of signaling pathways and transcription factors. The paper was conceived as a review of the data and ideas that have been formed to date on homeobox genes mutations that lead to the disruption of eye organogenesis and result in inherited eye/retinal diseases. Many of these diseases are part of the same clinical spectrum and have high genetic heterogeneity with already identified associated genes. We summarize the known key regulators of eye development, with a focus on the homeobox genes associated with monogenic eye diseases showing retinal manifestations. Recent advances in the field of genetics and high-throughput next-generation sequencing technologies, including single-cell transcriptome analysis have allowed for deepening of knowledge of the genetic basis of inherited retinal diseases (IRDs), as well as improve their diagnostics. We highlight some promising avenues of research involving molecular-genetic and cell-technology approaches that can be effective for IRDs therapy. The most promising neuroprotective strategies are aimed at mobilizing the endogenous cellular reserve of the retina.

Genetics of vesicoureteral reflux and congenital anomalies of the kidney and urinary tract

The definition of congenital anomalies of the kidney and urinary tract (CAKUT) is the disease of structural malformations in the kidney and/or urinary tract containing vesicoureteral reflux (VUR). These anomalies can cause pediatric chronic kidney disease. However, the pathogenesis of CAKUT is not well understood, because identifying the genetic architecture of CAKUT is difficult due to the phenotypic heterogeneity and multifactorial genetic penetrance. We describe the current genetic basis and mechanisms of CAKUT including VUR via approaching the steps and signaling pathways of kidney developmental processes. We also focus on the newly developed strategies and challenges to fully address the role of the associated genes in the pathogenesis of the disease.

Genetics of Vesicoureteral Reflux

Vesicoureteral reflux (VUR) is the retrograde passage of urine from the bladder to the upper urinary tract. It is the most common congenital urological anomaly affecting 1-2% of children and 30-40% of patients with urinary tract infections. VUR is a major risk factor for pyelonephritic scarring and chronic renal failure in children. It is the result of a shortened intravesical ureter with an enlarged or malpositioned ureteric orifice. An ectopic embryonal ureteric budding development is implicated in the pathogenesis of VUR, which is a complex genetic developmental disorder. Many genes are involved in the ureteric budding formation and subsequently in the urinary tract and kidney development. Previous studies demonstrate an heterogeneous genetic pattern of VUR. In fact no single major locus or gene for primary VUR has been identified. It is likely that different forms of VUR with different genetic determinantes are present. Moreover genetic studies of syndromes with associated VUR have revealed several possible candidate genes involved in the pathogenesis of VUR and related urinary tract malformations. Mutations in genes essential for urinary tract morphogenesis are linked to numerous congenital syndromes, and in most of those VUR is a feature. The Authors provide an overview of the developmental processes leading to the VUR. The different genes and signaling pathways controlling the embryonal urinary tract development are analyzed. A better understanding of VUR genetic bases could improve the management of this condition in children.

Detection of PAX2 deletions and duplications using multiplex ligation-dependent probe amplification

BACKGROUND

Renal coloboma syndrome (RCS) is a rare inherited disorder caused by mutations in the PAX2 gene. Clinical testing is currently performed by bidirectional Sanger sequencing of all 12 coding exons of the PAX2 gene, which detects point mutations or small insertion/deletion mutations. Large genomic deletions of PAX2 have been identified in 3/90 known RCS families, accounting for approximately (3%) of RCS cases. In these cases, the deletion was detected by cytogenetic techniques such as G-banding or array comparative genomic hybridization. While these methods would be sufficient to identify whole gene deletions, they may not be able to identify smaller rearrangements affecting single exons. Similarly, such deletions would not be detected by Sanger sequencing.

AIM

The aim of this study was to determine whether mutation-negative RCS probands harbor a genomic deletion or duplication involving one or more exons of the PAX2 gene. We evaluated this hypothesis in 46 patients with a clinical suspicion of RCS in whom no mutations were identified.

RESULTS

We developed a multiplex ligation-dependent probe amplification assay to detect gene deletion/duplication in all 12 exons of the PAX2 gene. Of the 46 PAX2 mutation-negative samples tested, none demonstrated deletions or duplications in the PAX2 gene. This suggests that deletions or duplications in PAX2 are unlikely to significantly contribute to the pathogenesis of RCS, beyond the known 3% of cases that have been attributed to whole gene deletions. Given these results, we hypothesize that other genes and/or locus control regions regulating PAX2 may be involved in the pathogenesis of PAX2 mutation-negative cases of RCS.

Genetics of vesicoureteral reflux

Primary vesicoureteral reflux (VUR) is the most common urological anomaly in children, affecting 1-2% of the pediatric population and 30-40% of children presenting with urinary tract infections (UTIs). Reflux-associated nephropathy is a major cause of childhood hypertension and chronic renal failure. The hereditary and familial nature of VUR is well recognized and several studies have reported that siblings of children with VUR have a higher incidence of reflux than the general pediatric population. Familial clustering of VUR implies that genetic factors have an important role in its pathogenesis, but no single major locus or gene for VUR has yet been identified and most researchers now acknowledge that VUR is genetically heterogeneous. Improvements in genome-scan techniques and continuously increasing knowledge of the genetic basis of VUR should help us to further understand its pathogenesis.