Table 3. Similarity of skeletal features found in human achondroplasia and observed in achondroplasia mouse models.

Skeletal features of human achondroplasia	Tg mFgfrACH	KI mFgfr3ACH	Tg hFGFR3ACH	KI hFGFR3ACH
Rhizomelic dwarfism at birth	NS	NS	At birtha	At birth
Large head with frontal bossing, mid-face hypoplasia at birth	21 days	10 days	At birth	At birth
Craniosynostosis at birth	ND	ND	ND	At birth
Low bone density in adolescent and adult	ND	ND	ND	At birth
Homozygous ACH patients are stillborn or die during the neonatal period	ND	ND	Die soon after birth	A higher mortality rate at birth
Thoracic kyphosis by 4 months	1 month	5 weeks	ND	1 month
Narrow growth plate	10 days	1 month	At birth	1 month

Tg mFgfr3^ACH, transgenic mice expressing mouse Fgfr3^G374R using the type II collagen promoter and enhancer sequences¹⁰. KI mFGFR3^ACH, gene targeting mouse Fgfr3^G374R 8. Tg hFGFR3^ACH, transgenic mice expressing human FGFR3^G380R using the mouse Fgfr3 promoter¹¹. KI hFGFR3^ACH, gene targeting human FGFR3^G380R as described in this report. ND, not described; NS, not significant.

^aThe time point when the specific phenotype was first observed in each ACH mouse model.