PLS3 sequencing in childhood-onset primary osteoporosis identifies two novel disease-causing variants

Abstract

SummaryAltogether 95 children with primary bone fragility were screened for variants in PLS3, the gene underlying X-linked osteoporosis. Two children with multiple peripheral and spinal fractures and low BMD had novel disease-causing PLS3 variants. Children with milder phenotypes had no pathogenic variants. PLS3 screening is indicated in childhood-onset primary osteoporosis.IntroductionThe study aimed to determine the role of pathogenic PLS3 variants in children’s bone fragility and to elucidate the associated phenotypic features.MethodsTwo cohorts of children with bone fragility were screened for variants in PLS3, the gene underlying X-linked osteoporosis. Cohort I comprised 31 patients with childhood-onset primary osteoporosis of unknown etiology. Cohort II comprised 64 children who had sustained multiple fractures but were otherwise healthy. Clinical and radiological data were reviewed. Peripheral blood DNA was Sanger sequenced for coding exons and flanking intronic regions of PLS3.ResultsIn two patients of cohort I, where other common genetic causes had been excluded, we identified two novel disease-causing PLS3 variants. Patient 1 was a male with bilateral femoral fractures at 10 years, low BMD (Z-score −4.1; 18 years), and multiple vertebral compression fractures. He had a novel nonsense variant in PLS3. Patient 2 was a girl with multiple long bone and vertebral fractures and low BMD (Z-score −6.6 at 6 years). She had a de novo missense variant in PLS3; whole exome sequencing and array-CGH identified no other genetic causes. Iliac crest bone biopsies confirmed low-turnover osteoporosis in both patients. In cohort II, no pathogenic PLS3 variants were identified in any of the subjects.ConclusionsTwo novel disease-causing variants in PLS3 were identified in a boy and a girl with multiple peripheral and spinal fractures and very low BMD while no pathogenic variants were identified in children with less severe skeletal fragility. PLS3 screening is warranted in male and female patients with childhood-onset primary osteoporosis.Electronic supplementary materialThe online version of this article (doi:10.1007/s00198-017-4150-9) contains supplementary material, which is available to authorized users.

Rare copy number variants in array-based comparative genomic hybridization in early-onset skeletal fragility

“…On the other hand, SNVs and deletions in PLS3 have already been reported in patients with osteoporosis (39)(40)(41)(42)(43). Recently, some patients with PLS3 deletions have been described, and apart from severe osteoporosis there is a bone mineralization defect (42).…”

Biomarkers in WNT1 and PLS3 Osteoporosis: Altered Concentrations of DKK1 and FGF23

“…We recruited PLS3 mutation‐positive subjects from four previously identified Finnish families with different PLS3 mutations: Family C, an intronic splice site mutation c.73–24T>A (p.Asp25Alafs*17); Family D, a 12.5‐kilobase (kb) tandem duplication spanning intron 2 to 3 of PLS3 ; Family E, a nonsense mutation c.766C>T (p.Arg256*); and Family F, a de novo heterozygous missense mutation c.1424A>G (p.Asn446Ser) . We offered participation to all mutation‐positive individuals ( n = 14, n = 3, n = 2, n = 1, respectively) in these four families.…”

“…We have previously, in our prior studies on monogenic forms of osteoporosis, identified the same WNT1 mutation in two unrelated Finnish families and four different PLS3 mutations in four Finnish families . These were identified using different methods, including targeted Sanger sequencing, whole‐genome sequencing, and custom‐made array‐comparative genomic hybridization . In the current study, we screened all participating study subjects for the pertinent gene mutation with conventional Sanger sequencing on DNA extracted from peripheral blood as described …”

“…The mutated WNT1 leads to low activation of the WNT pathway, decreased expression of target genes, and consequently low bone turnover, low bone mineral density (BMD), and prevalent fractures . Similarly, in 2013, mutations in plastin 3–encoding PLS3 , were reported to result in X‐linked childhood‐onset osteoporosis with frequent peripheral and vertebral compression fractures and low bone turnover with heterogenous and defective mineralization in bone biopsies . Due to its X‐chromosomal inheritance pattern, the phenotype is typically more severe in affected males, whereas females have normal to increased skeletal fragility …”

“…Vertebral fractures are a common feature in both WNT1 and PLS3 osteoporosis, whereas the incidence of peripheral fractures varies. DXA‐derived BMD values range from normal to severely reduced depending on patient age, gender, and type of mutation . Furthermore, despite the distinct skeletal pathologies, conventional metabolic bone markers have been reported to be normal in affected WNT1 and PLS3 mutation‐positive subjects .…”