Identification of intragenic deletions and duplication in the FLCN gene in Birt-Hogg-Dubé syndrome†

Birt-Hogg-Dube syndrome(BHDS), caused by germline mutations in the folliculin (FLCN) gene, predisposes individuals to develop fibrofolliculomas, pulmonary cysts, spontaneous pneumothoraces and kidney cancer. The FLCN mutation detection rate by bidirectional DNA sequencing in the National Cancer Institute BHDS cohort was 88%. To determine if germline FLCN intragenic deletions/duplications were responsible for BHDS in families lacking FLCN sequence alterations, 23 individuals from 15 unrelated families with clinically-confirmed BHDS but no sequence variations were analyzed by real-time quantitative PCR (RQ-PCR) using primers for all 14 exons. Multiplex Ligation-Dependent Probe Amplification (MLPA) Assay and arraybased comparative genomic hybridization (CGH) were utilized to confirm and fine map the rearrangements. Long Range PCR followed by DNA sequencing was used to define the breakpoints. We identified 6 unique intragenic deletions in 9 patients from 6 different BHDS families including four involving exon 1, one that spanned exons 2–5, and one that encompassed exons 7–14 of FLCN. Four of the six deletion breakpoints were mapped, revealing deletions ranging from 5688 to 9189bp. In addition, one 1341bp duplication, which included exons 10 and 11, was identified and mapped. This report confirms that large intragenic FLCN deletions can cause BHDS and documents the first large intragenic FLCN duplication in a BHDS patient.