BACKGROUND: The RET gene encodes a tyrosine kinase receptor involved in 
different human neurocristopathies, such as specific neuroendocrine tumours and 
Hirschsprung disease (HSCR). Gene expression is developmentally regulated and 
the RET transcript is undetectable in most adult cells, including lymphocytes. 
The impossibility of performing functional studies on RET mRNA has to date 
limited the detection and characterisation of an indefinite proportion of gene 
anomalies that cannot be identified by conventional DNA genomic screening in 
HSCR cases.
AIMS: Development of a protocol suitable to activate RET expression in RET 
negative cell lines and therefore to investigate directly RET mRNA, extending 
the conventional gene mutation analysis to detection of splicing anomalies and 
impaired expression of the RET gene.
METHODS: The effect of sodium butyrate (NaB), a histone deacetylase inhibitor, 
on rescuing RET expression was tested by one round of reverse transcription- 
polymerase chain reaction from total RNA of treated lymphoblasts from both HSCR 
patients and control individuals.
RESULTS: Analysis of RET expression was possible by NaB treatment of RET 
negative cells, such as lymphoblasts. This treatment allowed us to detect 
impaired RET expression as well as a splicing defect in two HSCR patients 
previously believed to be devoid of any gene abnormality.
CONCLUSIONS: The full application of the proposed protocol in most of the 
unexplained HSCR cases will allow us to establish the precise role of RET not 
only in causing but also in predisposing to HSCR pathogenesis.