Germ-line deletion in DICER1 revealed by a novel MLPA assay using synthetic oligonucleotides.

DICER1 is an endoribonuclease responsible for the production of mature microRNAs which are small, single-stranded RNA molecules that regulate gene expression post-transcriptionally by binding to mRNA and repressing the expression of target genes. Germ-line mutations in DICER1 are responsible for a rare cancer syndrome, including tumors that can co-occur with multinodular goiter (MNG). Using Sanger sequencing, we screened all DICER1 exons and intron boundaries in 20 suspected mutation carriers: nine with ovarian sex cord-stromal tumors (including Sertoli-Leydig cell tumors (SLCTs)), five with pleuropulmonary blastoma, one with cystic nephroma, one with nasal chondromesenchymal hamartoma and four with more than one manifestation suggestive of a germ-line DICER1 mutation. All were negative for any apparently deleterious variants. We developed a Multiplex Ligation-based Probe Amplification assay for DICER1 to screen for large deletions or duplications. Synthetic oligonucleotides were designed to cover all exons in three probe-mixes. In a child with a SLCT and MNG, and in her mother and brother (both diagnosed with MNG), we identified a heterozygous germ-line deletion of approximately 3 kilobases that eliminates exon 21 of DICER1 and two-thirds of intron 21, accompanied by an insertion of a G nucleotide at the 3' end of the deletion (c.3270-6_4051-1280delinsG). This allele is expressed in the patient's cDNA, creating an out-of-frame deletion predicted to result in a truncated protein (r.3270_4050del; p.Tyr1091Ser*28). Our novel finding of a disease-causing large deletion in DICER1 emphasizes the need to include assays that can detect rearrangements, duplications and deletions in any DICER1 screening protocol.

High prevalence of primary ovarian insufficiency in girls and young women with Nijmegen breakage syndrome: evidence from a longitudinal study.

CONTEXT: Nijmegen breakage syndrome (NBS) is a severe chromosomal instability disorder characterized by microcephaly, growth retardation, immune deficiency, and predisposition for malignancy. It is caused by hypomorphic mutations in the NBN gene, which product belongs to the protein complex critical for processing DNA double-strand breaks during mitotic and meiotic recombination. Data on gonadal function in patients with NBS are limited. OBJECTIVE: Growth and sexual development, along with hormonal assays, were evaluated in girls and young women with NBS homozygous for c.657_661del5 mutation. STUDY DESIGN AND PATIENTS: The group comprised 37 girls and young women with NBS (ages, 0.17-24.25 yr), followed between 1993 and 2008. Patients were divided into three age groups: 1) 1-3 yr; 2) 4-9 yr; and 3) 10 yr and older. Growth, puberty, concentrations of gonadotropins and 17-beta-estradiol, bone age, and pelvic ultrasound were assessed. RESULTS: None of the patients presented a typical growth spurt; the adult height ranged between the 3rd and 25th centiles. Median bone age was delayed by 4.05 yr. Pubarche reached stadium P2 in eight patients and P3 in two patients. In all but one girl, thelarche did not exceed Th2, with low 17beta-estradiol levels. Gonadotropin levels showed a biphasic pattern, with median FSH values of 55.0, 10.9, and 81.9 IU/liter, and LH of 3.2, 0.8, and 21.0 IU/liter in consecutive age groups. Ultrasound visualized small ovaries or solid streaks and the hypoplastic uterus. CONCLUSIONS: Primary ovarian insufficiency and the associated hypergonadotropic hypogonadism are hallmark manifestations in girls and young women with NBS. Our findings emphasize the need for long-term endocrinological and interdisciplinary supervision of these patients.