The expression of RET and its multiple splice forms in developing human kidney

Abstract

A series of inductive events between two di erent cell groups, the ureteric bud epithelium and metanephric mesenchyme, gives rise to the functional mammalian kidney. These reciprocal inductive interactions involve a number of molecules, one of which is the RET receptor tyrosine kinase. The phenotype of mice lacking functional RET includes kidney agenesis or severe dysgenesis, indicating a requirement for RET in kidney organogenesis. To investigate RET expression in human kidney development, we used a semi-quantitative RT ± PCR-based strategy to examine a panel of kidney RNA samples ranging from 8 ± 24 weeks gestational age. We found RET expression was highest earlier in development (14 weeks) with expression decreasing through to 24 weeks gestation. While three alternative RET transcripts generated by exon skipping at the 5' end of the gene were all detected throughout kidney development, expression of one transcript, RET2/6, where exon 2 was spliced to exon 6, varied relative to full length RET during this period. Levels of RET2/6 were highest at the earliest age of fetal kidney examined (8 weeks) and decreased relative to all other RET transcripts to low adult levels. The period of high expression coincides with a period of rapid bud bifurcation. Thus, it is possible that RET2/6 has a role in the early growth and di erentiation of the human kidney.

Sex difference in immunostaining of RET in the adult mouse kidney

“…Recently, c-ret transcripts were detected in the adult human kidney (Ivanchuk et al, 1997) and we also found expression in adult mouse kidneys by RT ± PCR. Using in situ hybridization, we found ubiquitous localization of the transcript in the adult kidney.…”

“…Although RET was not detected in adult rat kidneys, alternative spliced transcripts were detected in the adult human kidney by using reverse transcription-polymerase chain reaction (RT ± PCR; Ivanchuk et al, 1997). Here we report the study of c-ret expression in embryonic, neonatal (day 7) and adult mouse kidneys.…”

Expression of RET 3′ splicing variants during human kidney development

“…RET is expressed in cells and tissues derived from the neural crest, branchial arches and kidney (Pachnis et al, 1993;Tahira et al, 1990). Expression is highest in early developmental stages decreasing to low adult levels (Avantaggiato et al, 1994;Durbec et al, 1996b;Ivanchuk et al, 1997;Pachnis et al, 1993). In situ hybridization studies have localized RET expression to the ureteric bud in embryonic murine kidney (Pachnis et al, 1993).…”

“…RET encodes multiple transcripts resulting from alternative splicing of 5' or 3' exons (Ivanchuk et al, 1997;Lorenzo et al, 1995;Myers et al, 1995;Tahira et al, 1990). Skipping of exons encoding the RET extracellular domain results in products with deletions within the putative ligand binding portion of the receptor or in a truncated soluble isoform (Ivanchuk et al, 1997;Lorenzo et al, 1995).…”

“…Skipping of exons encoding the RET extracellular domain results in products with deletions within the putative ligand binding portion of the receptor or in a truncated soluble isoform (Ivanchuk et al, 1997;Lorenzo et al, 1995). We have previously shown that expression of RET 5' alternatively spliced variants is developmentally regulated during human kidney organogenesis with one splice variant, where exon 2 is spliced to exon 6, showing a particularly strong pattern of developmental regulation (Ivanchuk et al, 1997). As yet, the function or signi®cance of these variant isoforms is unknown.…”