利钠肽受体2(NPR2)在软骨和骨形态发生中起关键作用。NPR2基因突变导致肢端间膜发育不良,Maroteaux型(AMDM),身材矮小伴非特异性骨骼异常(SNSK),骨phy软骨发育不良,三浦型(ECDM)。然而,致病机制尚不清楚。在我们的研究中,我们鉴定了一个从头(R557C)和六个新的变体(G602W,V970F,R767*,R363*,F857S,和Y306S)在五个独立的家庭矮小的中国家庭中。3例杂合子突变患者(G602W,V970F,和R767*)诊断为SNSK(身高SD评分范围为-2.25至-5.60),而另外两个具有复合杂合突变(R363*和F857S,R557C和Y306S)诊断为ADM(身高SD评分范围为-3.10至-5.35)。在三名杂合状态的患者中,两名在青春期开始前接受rhGH治疗的患者显着改善了他们的生长(身高速度7.2cm/年,6.0厘米/年),1例青春期患者对rhGH治疗反应不佳(身高速度2.5cm/年)。7个NPR2基因变异体构建并在HEK293T和ATDC5细胞中过表达,我们发现带有突变型NPR2基因的ATDC5细胞分化程度降低,如ColII的较低表达所证明,Colx,和BMP4和Sox9的更高表达。此外,表达突变型NPR2基因的ATDC5细胞凋亡率升高。N-糖基化修饰,质膜定位,内质网应激是由内质网突变蛋白的积累引起的,如GRP78和p-IRE1α的较高表达所示。总的来说,我们的结果为NPR2功能丧失提供了新的见解,通过内质网应激和未折叠蛋白反应促进软骨细胞凋亡,抑制细胞分化。
Natriuretic peptide receptor 2 (
NPR2) plays a key role in cartilage and bone morphogenesis. The
NPR2 gene mutations result in acromesomelic dysplasia, Maroteaux type (AMDM), short stature with nonspecific skeletal abnormalities (SNSK), and epiphyseal chondrodysplasia, Miura type (ECDM). However, the pathogenic mechanism remains unclear. In our study, we identified one de novo (R557C) and six novel variants (G602W, V970F, R767*, R363*, F857S, and Y306S) in five independent Chinese families with familial short stature. Three patients with heterozygous mutations (G602W, V970F, and R767*) were diagnosed with SNSK (height SD score ranged from -2.25 to -5.60), while another two with compound heterozygous mutations (R363* and F857S, R557C and Y306S) were diagnosed with AMDM (height SD score ranged from -3.10 to -5.35). Among three patients with heterozygous status, two patients before puberty initiation with rhGH treatment significantly improved their growth (height velocity 7.2 cm/year, 6.0 cm/year), and one patient in puberty had a poor response to the rhGH treatment (height velocity 2.5 cm/year). Seven
NPR2 gene variants were constructed and overexpressed in HEK293T and ATDC5 cells, and we found that ATDC5 cells with mutant
NPR2 gene showed decreased differentiation, as evidenced by lower expression of ColII, ColX, and BMP4 and higher expression of Sox9. Moreover, the apoptosis rate was elevated in ATDC5 cells expressing the mutant
NPR2 gene. N-glycosylation modification, plasma membrane localization, and ER stress resulted from the accumulation of mutant protein in ER, as shown by the higher expression of GRP78 and p-IRE1α. Overall, our results provide a novel insight into NPR2 loss of function, which could promote chondrocyte apoptosis and repress cell differentiation through ER stress and the unfolded protein response.