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Urofacial (also called Ochoa) syndrome (UFS) is an autosomal recessive congenital disorder of the urinary bladder featuring voiding dysfunction and a grimace upon smiling. Biallelic variants in HPSE2, coding for the secreted protein heparanase-2, are described in around half of families genetically studied. Hpse2 mutant mice have aberrant bladder nerves. We sought to expand the genotypic spectrum of UFS and make insights into its pathobiology. Sanger sequencing, next generation sequencing and microarray analysis were performed in four previously unreported families with urinary tract disease and grimacing. In one, the proband had kidney failure and was homozygous for the previously described pathogenic variant c.429T>A, p.(Tyr143*). Three other families each carried a different novel HPSE2 variant. One had homozygous triplication of exons 8 and 9; another had homozygous deletion of exon 4; and another carried a novel c.419C>G variant encoding the missense p.Pro140Arg in trans with c.1099-1G>A, a previously reported pathogenic splice variant. Expressing the missense heparanase-2 variant in vitro showed that it was secreted as normal, suggesting that 140Arg has aberrant functionality after secretion. Bladder autonomic neurons emanate from pelvic ganglia where resident neural cell bodies derive from migrating neural crest cells. We demonstrated that, in normal human embryos, neuronal precursors near the developing hindgut and lower urinary tract were positive for both heparanase-2 and leucine rich repeats and immunoglobulin like domains 2 (LRIG2). Indeed, biallelic variants of LRIG2 have been implicated in rare UFS families. The study expands the genotypic spectrum in HPSE2 in UFS and supports a developmental neuronal pathobiology.

Kidney malformations are common causes of chronic renal failure in children. Dysplastic kidneys represent a unique model of perturbed epithelialmesenchymal interaction which leads to the formation of malformed branching tubules surrounded by undifferentiated and metaplastic mesenchymal cells. We have found that human dysplastic epithelia express PAX2 (a transcription factor), BCL2 (a survival factor) and galectin-3 (a cell adhesionlsignaling molecule). These genes are implicated in oncogenesis and their persistent expression may drive proliferation of dysplastic cysts, hence explaining the massive growth of some multicystic dysplastic kidneys. We have also detected prominent apoptosis in undifferentiated tissues around dysplastic epithelia, and this may provide a potential mechanism for the well-documented regression of dysplastic kidneys. Hence, although these kidneys may not have any excretory function, it is incorrect to consider them as 'end stage organs' because they are highly active in terms of cell turnover and gene expression; furthermore, these processes can be correlated with patterns of tissue growth and involution. Further elucidation of 'molecular lesions' in renal malformations may lead to novel therapies to enhance the differentiation of progenitor cells.