Idiopathic short stature due to novel heterozygous mutation of the aggrecan gene.

BACKGROUND: Recently, whole exome sequencing identified heterozygous defects in the aggrecan (ACAN) gene in three families with short stature and advanced bone age. OBJECTIVE: We report a novel frameshift mutation in ACAN in a family with dominantly inherited short stature, advanced bone age, and premature growth cessation. This is the first case of targeted sequencing of ACAN in this phenotype and confirms that ACAN sequencing is warranted in patients with this rare constellation of findings. RESULTS: We present a 5 1/2-year-old male with a family history of short stature in three generations. The maternal grandfather stands 144.5 cm (Ht SDS -4.7), mother 147.7 cm (Ht SDS -2.6), and index case 99.2 cm (Ht SDS -2.7). Our prepubertal patient has significant bone age advancement (bone age 8 years at chronologic age 5 1/2 years) resulting in a poor predicted adult height of 142 cm (Ht SDS -5.1). DNA sequencing identified a novel heterozygous variant in ACAN, which encodes aggrecan, a proteoglycan in the extracellular matrix of growth plate and other cartilaginous tissues. The mutation (p.Gly1797Glyfs*52) results in premature truncation and presumed loss of protein function. CONCLUSION: Mutations in the ACAN gene should be included in the differential diagnosis of the child with idiopathic short stature or familial short stature and bone age advancement.

Central precocious puberty caused by mutations in the imprinted gene MKRN3.

BACKGROUND: The onset of puberty is first detected as an increase in pulsatile secretion of gonadotropin-releasing hormone (GnRH). Early activation of the hypothalamic-pituitary-gonadal axis results in central precocious puberty. The timing of pubertal development is driven in part by genetic factors, but only a few, rare molecular defects associated with central precocious puberty have been identified. METHODS: We performed whole-exome sequencing in 40 members of 15 families with central precocious puberty. Candidate variants were confirmed with Sanger sequencing. We also performed quantitative real-time polymerase-chain-reaction assays to determine levels of messenger RNA (mRNA) in the hypothalami of mice at different ages. RESULTS: We identified four novel heterozygous mutations in MKRN3, the gene encoding makorin RING-finger protein 3, in 5 of the 15 families; both sexes were affected. The mutations included three frameshift mutations, predicted to encode truncated proteins, and one missense mutation, predicted to disrupt protein function. MKRN3 is a paternally expressed, imprinted gene located in the Prader-Willi syndrome critical region (chromosome 15q11-q13). All affected persons inherited the mutations from their fathers, a finding that indicates perfect segregation with the mode of inheritance expected for an imprinted gene. Levels of Mkrn3 mRNA were high in the arcuate nucleus of prepubertal mice, decreased immediately before puberty, and remained low after puberty. CONCLUSIONS: Deficiency of MKRN3 causes central precocious puberty in humans. (Funded by the National Institutes of Health and others.).