Table 4.

Animal studies focused on primary cilium in osteocytes

Targeted cells	Genotype	Baseline skeletal phenotype	External stimulation		Ref.
			Mechanical	Chemical
Global
Pkd1−/−		Embryonic lethal.	n/a	n/a	68
Pkd1m1Bei/miBei		Embryonic lethal; delayed endochondral and intramembranous bone formation through inhibition of Runx2 expression.	n/a	n/a	68
Pkd1+/m1bei		Reduced mineral density, mineral apposition rate, reduced osteoblast marker expression (Osteocalcin, Osterix, Opg, Rankl), osteoclast marker expression (TRAP).	n/a	n/a	68
Spef2−/−		Significantly shorter tibiae and femora length, with reduced skull bone thickness at P15, lower bone density for both trabecular and cortical bone (Th10 and L2 vertebrae and distal femur), and lower mechanical properties; osteoblast differentiation is impaired in the Spef2-KO mice with lower Alp, Runx2, Col1, and Osteocalcin expressions.	n/a	n/a	73
AC6−/−		Normal bone morphology.	Impaired responses to mechanical loading; mice lacking AC6 had 41% lower bone formation compared with control animals; primary bone cells isolated from AC6-null mice had an attenuated flow induced increase in Cox-2 mRNA expression.	Similar bone formation in responses to osteogenic chemical agents (PTH).	76
Osteoblasts and osteocytes
Cola1(I) 2.3-Cre; Kif3afl/fl		No differences in embryo size, limb patterning, nor growth plate architecture at E16.5–18.5, and even no effect on skeletal morphology, bone density, nor bone quality in adult animals.	Skeletally mature (16 weeks old) Cola1(I) 2.3-Cre; Kif3afl/fl mice exhibit less responsiveness to mechanical ulna loading compared with control mice; displayed significant less bone formation in dynamic histomorphometry analysis.	n/a	74
OC-Cre; Kif3afl/fl		Developed osteopenia by 6 weeks of age; reductions in femoral bone mineral density (22%), trabecular bone volume (42%) and cortical thickness (17%); impaired osteoblast function.	n/a	n/a	75

Ref. references, n/a not available