Phenotypes associated with this allele

• Allele Symbol: Fgf8^tm1.2Mrt
• Allele Name: targeted mutation 1.2, Gail R Martin
• Allele ID: MGI:2150346
• Summary: 7 genotypes

Jump to	Allelic Composition	Genetic Background	Genotype ID
hm1	Fgf8^tm1.2Mrt/Fgf8^tm1.2Mrt	involves: 129P2/OlaHsd	MGI:2176812
ht2	Fgf8^tm1.1Mrt/Fgf8^tm1.2Mrt	involves: 129P2/OlaHsd	MGI:2176815
ht3	Fgf8^tm1.2Mrt/Fgf8^tm1.3Mrt	involves: 129P2/OlaHsd	MGI:2176818
ht4	Fgf8^tm1.2Mrt/Fgf8^tm1.4Mrt	involves: 129P2/OlaHsd	MGI:2176824
cn5	Fgf8^tm1.2Mrt/Fgf8^tm1.3Mrt Foxg1^tm1(cre)Skm/Foxg1^+	involves: 129P2/OlaHsd	MGI:3720595
cn6	Fgf8^tm1.2Mrt/Fgf8^tm1.3Mrt Tg(Nes-cre)1Atp/0	involves: 129P2/OlaHsd * FVB/N	MGI:2176845
cx7	Chd7^Gt(XK403)Byg/Chd7^+ Fgf8^tm1.2Mrt/Fgf8^+	either: (involves: 129P2/OlaHsd * C57BL/6) or (involves: 129P2/OlaHsd * CD-1)	MGI:4410379

Genotype
MGI:2176812

hm1

• Allelic Composition: Fgf8^tm1.2Mrt/Fgf8^tm1.2Mrt
• Genetic Background: involves: 129P2/OlaHsd

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

mortality/aging

embryonic lethality during organogenesis, complete penetrance ( J:45909 )

• all homozygotes are resorbed by E10.5

• by E9.5 embryos begin to die likely because the heart does not form

embryo

abnormal ectoderm development ( J:56519 )

• ectoderm on the anterior side of the embryo appears undifferentiated and fails to form a neural tube

abnormal mesoderm development ( J:45909 , J:56519 )

• all embryonic mesoderm-derived structures appear to be absent including the heart (J:45909)

• at E8.5 embryos lack all mesodermally-derived tissues including the heart and somites; little mesoderm is detected anterior to the primitive streak (J:56519)

decreased embryo size ( J:45909 )

• embryos are significantly smaller than wild-type or heterozygous littermates at E8.5 and E9.5

abnormal embryonic epiblast morphology ( J:56519 )

• after cells undergo epithelial-mesenchymal transition, at E7.5, majority of nascent mesodermal cells fail to migrate away from the primitive streak, resulting in deformation of the epiblast and inward collapse of the posterior side of the embryo

absent primitive node ( J:56519 )

• node does not form in mutants

absent somites ( J:56519 )

• somites do not develop

abnormal primitive streak elongation ( J:56519 )

• at E7.5 in mutant embryos the streak never extends to the distal tip of the embryo

abnormal allantois morphology ( J:56519 )

• allantois is displaced anteriorly

abnormal amnion morphology ( J:56519 )

abnormal chorion morphology ( J:56519 )

• a chorion can be identified but is often tortuous

growth/size/body

decreased embryo size ( J:45909 )

• embryos are significantly smaller than wild-type or heterozygous littermates at E8.5 and E9.5

cardiovascular system

absent heart ( J:45909 , J:56519 )

• the heart does not form (J:45909)

Genotype
MGI:2176815

ht2

• Allelic Composition: Fgf8^tm1.1Mrt/Fgf8^tm1.2Mrt
• Genetic Background: involves: 129P2/OlaHsd

mortality/aging

prenatal lethality, incomplete penetrance ( J:45909 )

• at E18.5, only 50% of the expected number of compound heterozygotes are found

growth/size/body

decreased embryo size ( J:45909 )

• embryos are categorized into 3 groups determined by severity of phenotype; embryos are generally smaller than wild-type littermates in the least severely affected group 1

• in group 2, embryos are very small and developmentally delayed compared to littermates but mesoderm-derived structures are present

• group 3 embryos which are the most severely affected group resemble Fgf8^tm1.2Mrt homozygotes

embryo

abnormal rostral-caudal axis patterning ( J:45909 )

• many group 2 embryos display a failure of posterior development

decreased embryo size ( J:45909 )

• embryos are categorized into 3 groups determined by severity of phenotype; embryos are generally smaller than wild-type littermates in the least severely affected group 1

• in group 2, embryos are very small and developmentally delayed compared to littermates but mesoderm-derived structures are present

• group 3 embryos which are the most severely affected group resemble Fgf8^tm1.2Mrt homozygotes

nervous system

abnormal pituitary gland morphology ( J:178252 )

• mutants exhibit severe abnormalities in the pituitary gland

• at E17.5, 2 of 6 mutants show a substantial reduction of anterior pituitary tissue and absence of the posterior lobe while 4 of 6 mutants show a mild pituitary gland phenotype

small embryonic telencephalon ( J:45909 )

• vesicles are abnormally small in group 1 embryos

abnormal midbrain morphology ( J:45909 )

• defects are usually more severe than in Fgf^tm1.1 homozygotes

absent inferior colliculus ( J:45909 )

• inferior collicular (posterior midbrain) tissue is deleted in group 1 embryos

abnormal hypothalamus morphology ( J:178252 )

• reduction of arginine vasopressin and oxytocin neurons in the supraoptic, suprachiasmatic, and paraventricular nuclei

absent cerebellum ( J:45909 )

• cerebellar tissue (anterior hindbrain) is absent in group 1 embryos; defects are usually more severe than in Fgf^tm1.1 homozygotes

cardiovascular system

abnormal heart development ( J:45909 )

• many group 2 embryos display cardiac abnormalities

limbs/digits/tail

syndactyly ( J:45909 )

• fusion of two digits is often observed

craniofacial

abnormal craniofacial development ( J:45909 )

endocrine/exocrine glands

abnormal pituitary gland morphology ( J:178252 )

• mutants exhibit severe abnormalities in the pituitary gland

• at E17.5, 2 of 6 mutants show a substantial reduction of anterior pituitary tissue and absence of the posterior lobe while 4 of 6 mutants show a mild pituitary gland phenotype

Genotype
MGI:2176818

ht3

• Allelic Composition: Fgf8^tm1.2Mrt/Fgf8^tm1.3Mrt
• Genetic Background: involves: 129P2/OlaHsd

normal phenotype

no abnormal phenotype detected ( J:45909 )

Genotype
MGI:2176824

ht4

• Allelic Composition: Fgf8^tm1.2Mrt/Fgf8^tm1.4Mrt
• Genetic Background: involves: 129P2/OlaHsd

mortality/aging

embryonic lethality during organogenesis, complete penetrance ( J:56519 )

• by E9.5 embryos begin to die likely because the heart does not form

embryo

abnormal ectoderm development ( J:56519 )

• ectoderm on the anterior side of the embryo appears undifferentiated and fails to form a neural tube

abnormal mesoderm development ( J:56519 )

• at E8.5 embryos lack all mesodermally-derived tissues including the heart and somites; little mesoderm is detected anterior to the primitive streak

abnormal embryonic epiblast morphology ( J:56519 )

• after cells undergo epithelial-mesenchymal transition, at E7.5, majority of nascent mesodermal cells fail to migrate away from the primitive streak, resulting in deformation of the epiblast and inward collapse of the posterior side of the embryo

absent primitive node ( J:56519 )

• node does not form in mutants

absent somites ( J:56519 )

• somites do not form

abnormal primitive streak elongation ( J:56519 )

• at E7.5 in mutant embryos the streak never extends to the distal tip of the embryo

abnormal allantois morphology ( J:56519 )

• allantois is displaced anteriorly

abnormal amnion morphology ( J:56519 )

• an amnion can be identified but is often tortuous

abnormal chorion morphology ( J:56519 )

• a chorion can be identified but is often tortuous

cardiovascular system

absent heart ( J:56519 )

• the heart does not form

Genotype
MGI:3720595

cn5

• Allelic Composition: Fgf8^tm1.2Mrt/Fgf8^tm1.3Mrt; Foxg1^tm1(cre)Skm/Foxg1⁺
• Genetic Background: involves: 129P2/OlaHsd

mortality/aging

perinatal lethality, complete penetrance ( J:122378 )

• mutant mice die at birth due to defects in forebrain development

nervous system

abnormal forebrain development ( J:122378 )

• at birth, mutants exhibit lethal defects in forebrain development

• however, overall development of the inner ear and cochlea appeared normal

hearing/vestibular/ear

abnormal cochlear sensory epithelium morphology ( J:122378 )

• at E18.5, IHCs and OHCs appear to be in direct contact with each other in some cochlear sections

abnormal pillar cell morphology ( J:122378 )

• at E18.5, mutant mice show a significant reduction in the size and number of pillar cells (PCs) relative to control mice

abnormal pillar cell differentiation ( J:122378 )

• at E18.5, the distance between the lateral edge of the IHC and the medial edge of the first row OHC (a measure of the degree of PC development) is significantly decreased along the length of the cochlea

• at E18.5, PCs with weak or no lumenal projections are noted along the entire cochlear length with no region-specific variations

absent pillar cells ( J:122378 )

• at E18.5, pillar cells are missing or underdeveloped

abnormal patterning of the organ of Corti ( J:122378 )

• at E18.5, lumenal surface of the organ of Corti shows disruption of pillar cell growth and close approximation of IHCs to OHCs

• however, the overall structure of the epithelium and putative developing pillar cells are normal up to E15

cellular

abnormal pillar cell differentiation ( J:122378 )

• at E18.5, the distance between the lateral edge of the IHC and the medial edge of the first row OHC (a measure of the degree of PC development) is significantly decreased along the length of the cochlea

• at E18.5, PCs with weak or no lumenal projections are noted along the entire cochlear length with no region-specific variations

Genotype
MGI:2176845

cn6

• Allelic Composition: Fgf8^tm1.2Mrt/Fgf8^tm1.3Mrt; Tg(Nes-cre)1Atp/0
• Genetic Background: involves: 129P2/OlaHsd * FVB/N

mortality/aging

neonatal lethality, complete penetrance ( J:58999 )

• mutants die shortly after birth; lungs do not inflate so death is probably from anoxia

embryo

small first pharyngeal arch ( J:58999 )

• at E9.0 the first branchial arch is smaller than in wild-type

cellular

increased apoptosis ( J:58999 )

• at E8.75-10 extensive cell death is observed; at E9.5 the region with dying cells stretches proximally to the trigeminal swelling and included the maxillary arch-forming region

craniofacial

abnormal craniofacial morphology ( J:58999 )

• mutants have severe craniofacial defects; some mutants show a less severe phenotype with a small increase in dermal bone development and abnormalities are often observed on only one side of the head

absent molars ( J:58999 )

• molars are absent but vestigal lower incisors are present in association with the rostral process

abnormal mandible morphology ( J:58999 )

• there is little expansion of the mandible primordia as embryos mature; growth is not completely arrested as the mandibular primordial extend distally and meet at the midline

abnormal maxilla morphology ( J:58999 )

• there is little expansion of the maxilla primordia as embryos mature

absent incus ( J:58999 )

• incus and ala temporalis fail to form

abnormal craniofacial development ( J:58999 )

• there is an ectodermal covering over the prospective mouth

absent Meckel's cartilage ( J:58999 )

• body of Meckel's cartilage fails to develop

small first pharyngeal arch ( J:58999 )

• at E9.0 the first branchial arch is smaller than in wild-type

decreased tongue size ( J:58999 )

• newborns have small disorganized tongues

nervous system

abnormal trigeminal nerve morphology ( J:58999 )

• the mandibular division of the trigeminal nerve is truncated and misrouted

hearing/vestibular/ear

absent incus ( J:58999 )

• incus and ala temporalis fail to form

digestive/alimentary system

decreased tongue size ( J:58999 )

• newborns have small disorganized tongues

skeleton

absent Meckel's cartilage ( J:58999 )

• body of Meckel's cartilage fails to develop

absent molars ( J:58999 )

• molars are absent but vestigal lower incisors are present in association with the rostral process

abnormal mandible morphology ( J:58999 )

• there is little expansion of the mandible primordia as embryos mature; growth is not completely arrested as the mandibular primordial extend distally and meet at the midline

abnormal maxilla morphology ( J:58999 )

• there is little expansion of the maxilla primordia as embryos mature

absent incus ( J:58999 )

• incus and ala temporalis fail to form

growth/size/body

absent molars ( J:58999 )

• molars are absent but vestigal lower incisors are present in association with the rostral process

decreased tongue size ( J:58999 )

• newborns have small disorganized tongues

Genotype
MGI:4410379

cx7

• Allelic Composition: Chd7^Gt(XK403)Byg/Chd7⁺; Fgf8^tm1.2Mrt/Fgf8⁺
• Genetic Background: either: (involves: 129P2/OlaHsd * C57BL/6) or (involves: 129P2/OlaHsd * CD-1)

cardiovascular system

abnormal fourth pharyngeal arch artery morphology ( J:154590 )

• in 26% of mice

craniofacial

abnormal fourth pharyngeal arch artery morphology ( J:154590 )

• in 26% of mice

embryo

abnormal fourth pharyngeal arch artery morphology ( J:154590 )

• in 26% of mice