ERN1 and Severe short stature: These morphometric and histological data indicate that the severity of the dwarfism caused by expression of the p.N617K collagen X in ColXN617K mice was not substantially altered by loss of XBP1 activity in C/X, revealing surprising redundancy for the IRE1/XBP1 pathway in the pathology of MCDS, and implying that XBP1-independent consequences of collagen X-induced ER stress must underpin the disease pathology.