All Phenotypes Flnb<tm1Vshn> MGI Mouse

preweaning lethality, incomplete penetrance ( J:125095 )

• only 7.7% of homozygotes are obtained within the first week of life, suggesting embryonic or early postnatal lethality

postnatal growth retardation ( J:125095 )

• male homozygotes show a significant decrease in postnatal growth rate relative to wild-type controls

• in contrast, female homozygotes show absence of clear growth and size differences

slow postnatal weight gain ( J:125095 )

• male, but not female, homozygotes never attain the size of adult wild-type controls by 8 weeks of age

abnormal neurocranium morphology ( J:125095 )

• dysmorphic calvaria

abnormal occipital bone morphology ( J:125095 )

• occipital bones are poorly calcified

abnormal parietal bone morphology ( J:125095 )

• parietal bones are poorly calcified

abnormal viscerocranium morphology ( J:125095 )

• dysmorphic facial bones

abnormal limb bone morphology ( J:125095 )

• limb bones are poorly calcified

abnormal radius morphology ( J:125095 )

• the radius appears less calcified and more fragile, as shown by von Kossa staining

• an increase in apoptosis is noted in the hypertrophic (H) zone of E16.5 radius, as shown by TUNEL analysis; increased rates of cell death occur along the periphery of the radius bones between E14.5 and E17.5, with dying cells restricted primarily to the perichondral regions, adjacent to the H zone

decreased diameter of radius ( J:125095 )

• the radius is thinned

short radius ( J:125095 , J:213355 )

	• radius length is reduced by ~1.4 mm at P1 and up to 4 mm by 8 weeks (J:213355)
	• the radius is significantly shorter at E16.5 and at 2 months (J:125095)

abnormal ulna morphology ( J:125095 )

• the ulna appears less calcified and more fragile, as shown by von Kossa staining

decreased diameter of ulna ( J:125095 )

• the ulna is thinned

abnormal patella morphology ( J:125095 )

• patellar bones are poorly calcified

decreased length of long bones ( J:213355 )

• at P1 to 8 weeks, appendicular long bones are shortened

brachyphalangia ( J:125095 )

• the phalanx (fore claw) is significantly shorter at E16.5 and at 2 months

abnormal thoracic cage morphology ( J:125095 )

• thoracic cages show increased radiolucency suggestive of osteopenia

rib fusion ( J:125095 )

• abnormal fusion of the proximal ribs in some mice

thin ribs ( J:125095 )

• ribs appear thin and gracile

small thoracic cage ( J:125095 )

kyphosis ( J:125095 )

• exaggerated thoracolumbar kyphosis in some mice

lordosis ( J:125095 )

• exaggerated lower thoracic lordosis in some mice

scoliosis ( J:125095 )

vertebral fusion ( J:125095 )

• female homozygotes display vertebral fusions

cervical vertebral fusion ( J:125095 )

• fusion of cervical spinal vertebrae in some mice

decreased bone mineral density ( J:125095 )

• micro-CT scans of mutant skeletons revealed a generalized mottled osteopenia at various developmental ages

decreased bone mineral density of vertebrae ( J:125095 )

• bone densitometry measurements of E20, P7 and adult vertebral segments revealed a significant reduction in bone density

abnormal chondrocyte morphology ( J:125095 , J:213355 )

• homozygotes show a progressive decline in the number of rapidly proliferating chondrocytes and premature differentiation characterized by an enlarged prehypertrophic zone, a widened Col2a1+/Col10a1+ (proliferative/hypertrophic) overlapping region, but a relatively reduced hypertrophic zone length (seen at P7 and at 2 weeks) (J:213355)

• early defect affecting hypertrophic chondrocyte differentiation within the more distal rather than proximal appendages (J:125095)

• the size of the prehypertrophic zone is variable and often blurred, as shown by Indian hedgehog staining (J:125095)

• a delay in chondrocyte progression and differentiation is seen in the H zone at 12 hr after the BrdU pulse, coinciding with a decrease in the length of the H zone of the E16.5 radius (J:125095)

• the greatest differences in the length of the H zone occur at E14.5 and E15.5, suggesting a delay in chondrocyte maturation and hypertrophy (J:125095)

abnormal perichondrium morphology ( J:125095 )

• increased apoptosis along the periphery of the hypetrophic (H) zone of the radius at E16.5; apoptotic cells reside within the perichondrium, adjacent to the H zone

• increased cell death is noted along the bone collar and is consistently seen through all skeletal developmental ages

abnormal skeleton development ( J:125095 )

• at E18.5, homozygotes display hypoplastic cartilaginous skeletons

• overall findings are consistent with a delay in skeletal development

abnormal long bone epiphyseal plate morphology ( J:213355 )

• at P7 to 2 weeks age, but not at P1, the ratio of Col10a1+ length relative to Col2a1+ length (hypertrophic to proliferative zone ratio), is decreased in the radius growth plate relative to that in wild-type controls (33.8% vs 45.3% at P7 and 71.9% vs 89.6% at 2 weeks, respectively), suggesting a delay in skeletogenesis

• at P1 and 2 weeks old age, but not at P7, the length of Col2a1+/Col10a1+ overlapping expression relative to the radius growth plate length is increased relative to that in wild-type controls (17.7% vs 8.6% at P1 and 24.2% vs 19.1% at 2 weeks, respectively)

• immunostaining of the growth plates with Pthr1 and Ihh (intermediate differentiation/prehypertrophic zone markers) revealed an increase in the prehypertrophic zone

• at P1, P7 and 2 weeks, the ratio of Pthr1+ length to growth plate length is increased relative to that in wild-type controls (51.7% vs 39.2% at P1, 38.7% vs 23.0% at P7, and 38.6% vs 28.1% at 2 weeks, respectively)

• at P7 and 2 weeks, the ratio of Ihh+ length to growth plate length is also increased (34.2% vs 19.6% at P7, and 37.0% vs 27.7% at 2 weeks)

abnormal long bone epiphyseal plate proliferative zone ( J:125095 , J:213355 )

• at P7, fewer Sox9+ labeled chondrocytes (i.e. less differentiated chondrocytes) are noted in the rapid proliferative zone and prehypertrophic zone relative to wild-type controls (47.8% vs 81.4%, respectively) (J:213355)

• at P7, signal intensity for Runx2 (a chondrocyte marker that is up-regulated during both endochondral and intramembranous ossification) is increased within chondrocyte progenitors in the proliferative zone relative to wild-type controls (32.6 vs 28.9 luminosity, respectively) (J:213355)

• at E14.5, E16.5 and P7, the % of cells positive for proliferation markers Sox9, BrdU (cells in S-phase), Ki67, and PH3 (cells in M-phase) is progressively decreased within the proliferative zone of the radius growth plate (J:213355)

• however, no increase in TUNEL staining is noted within the proliferative zone from E14.5 to P7 (J:213355)

• a slight decrease in the length and width of the proliferative (P) zone is observed by collagen II staining (J:125095)

• while proliferation in the P zone of E16.5 radius is largely unaffected (1 h post BrdU injection), the distribution of proliferating chondrocyte progenitors incorporating BrdU is shifted toward the resting zone (more distal to the H zone) (J:125095)

decreased width of hypertrophic chondrocyte zone ( J:125095 )

• the hypertrophic (H) zone is significantly shortened in length in both the radius and phalanx

• collagen X staining confirmed a clear reduction in the length and width of the H zone

• an increase in apoptosis is noted in the H zone of E16.5 radius, as shown by TUNEL analysis; increased rates of cell death occur along the periphery of the radius bones between E14.5 and E17.5, with dying cells restricted primarily to the perichondral regions, adjacent to the H zone

• the greatest differences in the length of the H zone occur at E14.5 and E15.5, suggesting a delay in chondrocyte maturation and hypertrophy

increased width of hypertrophic chondrocyte zone ( J:213355 )

• at P1, the relative thickness of the Col10a1+ hypertrophic zone (Col10a1+/whole growth plate ratio) is increased by 10% relative to that in wild-type controls (38.7% vs 28.5%, respectively), suggesting premature hypertrophic differentiation

• however, no significant change in the Col10a1+/whole growth plate ratio is noted at P7 and at 2 weeks, suggesting a slowing of the early maturation process over time

decreased long bone epiphyseal plate size ( J:125095 , J:213355 )

• at P1 and P7, the length of the growth plate in the radius is significantly shorter than that in wild-type controls (J:213355)

• H&E staining of E16.5 distal bone appendages revealed that mutant growth plates are significantly smaller than wild-type, as shown in the ulna, radius and phalanx (J:125095)

• the greatest reduction is observed in the more distal radius, ulna and digital bones, as opposed to the more proximal humerus (J:125095)

• however, no differences in chondrocyte size and shape, chondrocyte rotation and column integrity are seen (J:125095)

decreased bone mineralization ( J:125095 )

• whole skeleton preparations of E18.5 mutant embryos, stained with Alizarin red (bone) and Alcian blue (cartilage), show a decrease in bone mineralization

• micro-CT scans revealed demineralization of the mutant skeleton at various developmental ages (E20, P3, P13, P20 and adult)

• several of the trabecular and cortical bones (calvaria, patella and appendicular limbs) appear to be poorly calcified, as evidenced by the reduced radiolucency on CT scans

decreased bone ossification ( J:125095 )

• bone densitometry measurements of the vertebral segments revealed a significant reduction in bone ossification

delayed bone ossification ( J:125095 )

delayed endochondral bone ossification ( J:125095 )

• delayed endochondral ossification at E18.5

delayed intramembranous bone ossification ( J:125095 )

• delayed intramembranous ossification at E18.5

abnormal chondrocyte physiology ( J:125095 , J:213355 )

• in vivo, co-staining with Ki67 and BrdU revealed that the % of proliferating chondrocytes remaining in the G1/G0 phase (BrdU+, Ki67-/low) in the radius is increased by ~10% and ~13% at E16.5 and P7, respectively, relative to wild-type controls, indicating an increased number of actively proliferating chondrocytes adopting a more differentiated state (J:213355)

• in vitro, the % of proliferating chondrocytes remaining in G1/G0 (BrdU+, Ki67-/low) is increased by ~36%, relative to wild-type controls (J:213355)

• at E16.5, fewer phospho-beta1-integrin (Ser785) positive chondrocytes are observed in the mutant radius, indicating reduced chondrocyte cell adhesion (J:125095)

• mutant chondrocytes display decreased adhesion to several extracellular substrates including collagen and fibronectin, and show reduced binding to other ECM components (i.e. type IV collagen, vitronectin and laminin) (J:125095)

• at baseline, cultured mutant chondrocytes exhibit reduced cell spreading relative to wild-type chondrocytes (J:125095)

• decreased adhesion is further reduced by dominant negative beta1-integrin transfection relative to either mutant chondrocytes or wild-type chondrocytes transfected with the dominant negative beta1-integrin alone, indicating disruption of the ECM-integrin pathway through loss of cell adhesion (J:125095)

joint laxity ( J:125095 )

• female homozygotes display joint laxity