Spag17 Deficiency Results in Skeletal Malformations and Bone Abnormalities

Abstract

Height is the result of many growth and development processes. Most of the genes associated with height are known to play a role in skeletal development. Single-nucleotide polymorphisms in the SPAG17 gene have been associated with human height. However, it is not clear how this gene influences linear growth. Here we show that a targeted mutation in Spag17 leads to skeletal malformations. Hind limb length in mutants was significantly shorter than in wild-type mice. Studies revealed differences in maturation of femur and tibia suggesting alterations in limb patterning. Morphometric studies showed increased bone formation evidenced by increased trabecular bone area and the ratio of bone area to total area, leading to reductions in the ratio of marrow area/total area in the femur. Micro-CTs and von Kossa staining demonstrated increased mineral in the femur. Moreover, osteocalcin and osterix were more highly expressed in mutant mice than in wild-type mice femurs. These data suggest that femur bone shortening may be due to premature ossification. On the other hand, tibias appear to be shorter due to a delay in cartilage and bone development. Morphometric studies showed reduction in growth plate and bone formation. These defects did not affect bone mineralization, although the volume of primary bone and levels of osteocalcin and osterix were higher. Other skeletal malformations were observed including fused sternebrae, reduced mineralization in the skull, medial and metacarpal phalanges. Primary cilia from chondrocytes, osteoblasts, and embryonic fibroblasts (MEFs) isolated from knockout mice were shorter and fewer cells had primary cilia in comparison to cells from wild-type mice. In addition, Spag17 knockdown in wild-type MEFs by Spag17 siRNA duplex reproduced the shorter primary cilia phenotype. Our findings disclosed unexpected functions for Spag17 in the regulation of skeletal growth and mineralization, perhaps because of its role in primary cilia of chondrocytes and osteoblasts.

Mammalian axoneme central pair complex proteins: Broader roles revealed by gene knockout phenotypes

“…Other skeletal malformations include fused sternebrae, reduced mineralization in the skull, medial and metacarpal phalanges. Primary cilia from chondrocytes, osteoblasts, and embryonic fibroblasts (MEFs) are shorter and fewer cells have primary cilia in comparison to cells isolated from wild‐type mice [Teves et al, ]. Interestingly, an antibody against the C‐terminal domain of SPAG17 detected a ∼75 kDa protein expressed in MEFs, suggesting that it is an isoform of the 250 kDa full length protein.…”

A catalog of single nucleotide changes distinguishing modern humans from archaic hominins

“…RUNX2, EDAR, and GLI3(Adhikari et al 2016), NFATC1(Kim and Kim 2014), SPOP(Cai and Liu 2016), DDR2) and NELL1, possibly carrying changes in regulatory regions, while mutations in the HHMC-carrying gene encoding for the transcription factor ATRX cause facial dysmorphism(Moncini et al 2013). In addition, genes with HHMCs such as PLXNA2(Oh et al 2012), EVC2(Kwon et al 2018), MEPE(Gullard et al 2016), OMD(Tashima et al 2015), and SPAG17(Teves et al 2015) are known to affect craniofacial bone and tooth morphologies. These genes appear to be important in determining bone density, mineralization…”

A novel hypomorphic allele ofSpag17causes primary ciliary dyskinesia phenotypes in mice

“…The mammalian Spag17 gene shows greater complexity in expression patterns and functions (Teves, Nagarkatti-Gude et al 2016) than its orthologue pf6. Phenotypes beyond the motile cilia were also reported in the Spag17 mutant mice which develop skeletal defects with shorter and less frequent primary cilia on the Spag17 mutant chondrocytes, osteoblasts, and embryonic fibroblasts (MEFs; Teves, Sundaresan et al 2015). This is consistent with genome wide association studies suggested that SPAG17 may have a role in controlling human height trait (Weedon and Frayling 2008, Weedon, Lango et al 2008, Takeuchi, Nabika et al 2009, Kim, Lee et al 2010, Zhao, Li et al 2010, N'Diaye, Chen et al 2011, van der Valk, for the Early Growth Genetics et al 2014, Wood, Esko et al 2014.…”

“…Previous reports indicated that SPAG17 is required for normal primary cilia function as well as growth and elongation of the long bones in mouse (Teves, Sundaresan et al 2015). SPAG17 has also been linked to height in human studies (Weedon and Frayling 2008, Weedon, Lango et al 2008, N'Diaye, Chen et al 2011, van der Valk, for the Early Growth Genetics et al 2014, Wood, Esko et al 2014.…”

“…However, recent advances and more characterization of ciliopathy mutants indicated that motile and primary ciliopathies can overlap in the same animal model and/or human patients (Moore, Escudier et al 2006, Fliegauf, Benzing et al 2007, Ferkol and Leigh 2012, Bukowy-Bieryłło, Ziętkiewicz et al 2013. Characterization of the Spag17 knock out mice provided new evidence that motile and primary ciliopathies can overlap or develop in the same model organism (Teves, Zhang et al 2013), (Teves, Sundaresan et al 2015). SPAG17 mutations are reported to cause human PCD (Andjelkovic, Minic et al 2018) and variants in the gene have been linked to human height (Weedon and Frayling 2008, Weedon, Lango et al 2008, Takeuchi, Nabika et al 2009, Kim, Lee et al 2010, Zhao, Li et al 2010) and multiple goat body measurements (Zhang, Jiang et al 2019).…”