Phenotypes Associated with This Genotype

Genotype
MGI:3773045

• Allelic Composition: Lbx1^tm1Gld/Lbx1^tm1Gld
• Genetic Background: involves: 129S1/Sv * C57BL/6

• ♀: phenotype observed in females
• ♂: phenotype observed in males
• N: normal phenotype

mortality/aging

perinatal lethality, complete penetrance ( J:56498 )

• majority of mutants are born dead; a living mutant was born and died within 2 hours

muscle

muscle phenotype ( J:56498 )

N • deep muscles of back, intercostals muscles and ventral body wall muscles are comparable to wild-type and heterozygous littermates

N • tongue muscles and diaphragm muscle form in homozygotes

N • small differences are observed in distribution of muscle tissue within the diaphragm, but no significant difference is seen in overall organization of diaphragm; tongue muscle shows no significant difference in size or organization relative to wild-type newborns

abnormal muscle precursor cell migration ( J:56498 )

• at E9.5, muscle precursors (Pax 3-positive cells) are clustered in the trunk, beneath the ventrolateral lip of dermomyotome; at E10.5, no Pax 3-positive cells are observed in forelimbs, while an enlarged stream of cells is seen adjacent to ventral aspect of limb at posterior forelimb levels

• in hindlimbs at E10.5, precursors delaminate but do not migrate very far from ventral edge of dermomyotome

abnormal limb muscle morphology ( J:56498 )

• proximal forelimb flexors (those connecting humerus, radius, and ulna to carpal bones) are present, but truncated along proximodistal axis of limb; muscle tissue is present only at proximal end of bones, giving way to tendon midway between wrist and elbow, while at P0, skeletal muscle extends 75% of distance from elbow to wrist

abnormal myogenesis ( J:56498 )

• MyoD-positive cells are absent from hindlimbs in E13.5 embryos, with exception of anlage of gluteus medius and another unidentified muscle

• extensor muscle anlagen in forelimbs are absent at E13.5, while flexor muscles show substantial size reduction midway between wrist and elbow

absent hypaxial muscle ( J:56498 )

• all hindlimb muscles are absent, except for gluteus medius and one other unidentified hypaxial muscle in newborn mice

• all only 2 hindlimb suspension muscles (quadriceps lumborum, pubococcygeus) are retained in homozygotes, suggesting hypaxial derivation of other suspension muscles

• in forelimbs, all extensor muscles are absent, but some flexor muscles are present

• muscles on extensor side of scapula (muscles derived from dorsal muscle mass) are absent, but muscle on flexor side is present but reduced in size

decreased skeletal muscle mass ( J:56498 )

• newborn mice display severe reduction in muscle mass in shoulders, pelvic girdle and limb extremities

limbs/digits/tail

abnormal forelimb morphology ( J:56498 )

• forelimbs are hyperflexed and thinner than in wild-type neonates

abnormal hindlimb morphology ( J:56498 )

• severely reduced in girth in newborn mice

abnormal limb muscle morphology ( J:56498 )

• proximal forelimb flexors (those connecting humerus, radius, and ulna to carpal bones) are present, but truncated along proximodistal axis of limb; muscle tissue is present only at proximal end of bones, giving way to tendon midway between wrist and elbow, while at P0, skeletal muscle extends 75% of distance from elbow to wrist

cellular

abnormal muscle precursor cell migration ( J:56498 )

• at E9.5, muscle precursors (Pax 3-positive cells) are clustered in the trunk, beneath the ventrolateral lip of dermomyotome; at E10.5, no Pax 3-positive cells are observed in forelimbs, while an enlarged stream of cells is seen adjacent to ventral aspect of limb at posterior forelimb levels

• in hindlimbs at E10.5, precursors delaminate but do not migrate very far from ventral edge of dermomyotome