Leukocyte cDNA analysis of NSD1 derived from confirmed Sotos syndrome patients.

BACKGROUND: Haploinsufficiency of the NSD1 gene leads to Sotos syndrome (Sos), which is characterised by excessive growth, especially during childhood, distinct craniofacial features and variable degree of mental impairment. A wide spectrum of NSD1 mutations have been described in Sos patients, ranging from more than 100 different single nucleotide changes, to partial gene deletions, and to microdeletions of various sizes comprising the entire NSD1 locus.

OBJECTIVE: To investigate the NSD1 cDNA sequence in genetically confirmed Sos patients harbouring truncating and missense mutations.

METHOD: Total RNA was isolated from a 250 mul standard EDTA blood sample from nine genetically verified Sos patients, and subsequent reverse-transcribed into cDNA followed by PCR and direct sequencing of specific NSD1 cDNA sequences.

RESULTS: All nine mutations, including missense, nonsense and whole exon deletions, previously identified in genomic DNA, could confidently be detected in cDNA. Several NSD1 transcript splice variants were detected.

CONCLUSION: Despite the fact that Sos is caused by haploinsufficiency, NSD1 transcripts containing nonsense and frame shift mutations can be detected in leukocyte-derived cDNA. The possibility therefore exists that certain NSD1 mutations are expressed and contribute to the phenotypic variability of Sos. NSD1 cDNA analysis is likely to enhance mutation detection in Sos patients.