Could FISH on buccal smears become a new method of screening in children suspect of HNF1B anomaly?

HNF1B gene anomalies include renal development defects associated with cysts and are well known by pediatric nephrologists that ask for molecular analysis of this gene. Two types of genomic rearrangements are reported: mutation and more frequently deletion. Using microsatellites or CGH array the size of the deletion was found to be at least of 1.2 Mb including 15 genes among which HNF1B, leading to the diagnosis of chromosomal microdeletion. Fluorescent In Situ Hybridization (FISH) is a simple routinely performed technique, considered as the referring tool to diagnose microdeletion in genetic practice. We performed interphasic FISH on buccal smears from 6 patients known to have HNF1B deletion to valid our technique and to determine the size of the 17q12 deletion. All the patients were found to present a 17q12 microdeletion. Our results showed that FISH is a rapid, reliable and specific technique to diagnose 17q12 microdeletion and might be performed as non invasive sampling procedure useful in pediatric practice. In conclusion we propose to use interphasic FISH to screen pediatric patients presenting with renal abnormalities possibly linked to HNF1B anomaly. Molecular analysis and MLPA (Multiplex Ligand Probe Analysis) could be performed in cases with normal interphasic FISH to detect a point mutation of the gene or more rarely a single exon deletion.