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Signaling by the glial cell line-derived neurotrophic factor (GDNF)-RET receptor tyrosine kinase and SPRY1, a RET repressor, is essential for early urinary tract development. Individual or a combination of GDNF, RET and SPRY1 mutant alleles in mice cause renal malformations reminiscent of congenital anomalies of the kidney or urinary tract (CAKUT) in humans and distinct from renal agenesis phenotype in complete GDNF or RET-null mice. We sequenced GDNF, SPRY1 and RET in 122 unrelated living CAKUT patients to discover deleterious mutations that cause CAKUT. Novel or rare deleterious mutations in GDNF or RET were found in six unrelated patients. A family with duplicated collecting system had a novel mutation, RET-R831Q, which showed markedly decreased GDNF-dependent MAPK activity. Two patients with RET-G691S polymorphism harbored additional rare non-synonymous variants GDNF-R93W and RET-R982C. The patient with double RET-G691S/R982C genotype had multiple defects including renal dysplasia, megaureters and cryptorchidism. Presence of both mutations was necessary to affect RET activity. Targeted whole-exome and next-generation sequencing revealed a novel deleterious mutation G443D in GFRα1, the co-receptor for RET, in this patient. Pedigree analysis indicated that the GFRα1 mutation was inherited from the unaffected mother and the RET mutations from the unaffected father. Our studies indicate that 5% of living CAKUT patients harbor deleterious rare variants or novel mutations in GDNF-GFRα1-RET pathway. We provide evidence for the coexistence of deleterious rare and common variants in genes in the same pathway as a cause of CAKUT and discovered novel phenotypes associated with the RET pathway.

Epstein-Barr virus (EBV) hepatitis is an uncommon, almost always self-limited disease in immunocompetent patients. Accurate diagnosis is imperative for appropriate clinical management. The aim of this study was to compare 3 available methods for EBV detection on routinely processed liver biopsies to determine their effectiveness in aiding the diagnosis. In 6 of the 8 cases of EBV hepatitis, EBV was detected by both polymerase chain reaction (PCR) for EBV DNA and in situ hybridization (ISH) for EBV early RNA (EBER). EBV was detected by PCR only in 1 case, and by ISH only in another. EBER-positive cells detected by ISH were typically few and individually distributed in the portal tracts and sinusoids. Immunohistochemical staining for EBV latent membrane proteins was negative in all 8 cases. Five cases of chronic hepatitis C used as negative controls were negative by all 3 detection methods for EBV. These data indicate that PCR and ISH are equally sensitive in detecting EBV in routinely processed liver biopsies. The ready implementation of ISH in pathology laboratories makes it a useful ancillary tool in confirming the diagnosis of EBV hepatitis in equivocal cases. However, EBER-positive cells can be sparse and easily overlooked. Immunohistochemistry for EBV latent membrane proteins apparently has no utility in the diagnosis of EBV hepatitis.