Phenotypes associated with this allele

• Allele Symbol: Chrnb2^tm1Mdb
• Allele Name: targeted mutation 1, Mariella De Biasi
• Allele ID: MGI:2158714
• Summary: 4 genotypes

Jump to	Allelic Composition	Genetic Background	Genotype ID
hm1	Chrnb2^tm1Mdb/Chrnb2^tm1Mdb	involves: 129S7/SvEvBrd	MGI:5318690
hm2	Chrnb2^tm1Mdb/Chrnb2^tm1Mdb	involves: 129S7/SvEvBrd * C57BL/6J	MGI:2663180
cx3	Chrnb2^tm1Mdb/Chrnb2^tm1Mdb Chrnb4^tm1Mdb/Chrnb4^tm1Mdb	involves: 129S7/SvEvBrd * C57BL/6J	MGI:2663179
cx4	Chrna7^tm1Bay/Chrna7^tm1Bay Chrnb2^tm1Mdb/Chrnb2^tm1Mdb	involves: 129S7/SvEvBrd * C57BL/6J	MGI:4822560

Genotype
MGI:5318690

hm1

• Allelic Composition: Chrnb2^tm1Mdb/Chrnb2^tm1Mdb
• Genetic Background: involves: 129S7/SvEvBrd

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

nervous system

abnormal lateral geniculate nucleus morphology ( J:139123 )

• ipsilateral retinogeniculate projections remain widespread in the dorsal lateral geniculate through 12 days of age

vision/eye

vision/eye phenotype ( J:139123 )

N • periodic retinal discharges are present as early as 2 days of age in Multi Electrode Recordings

abnormal eye electrophysiology ( J:139123 )

• wave and spike frequencies are greater than controls

• retinal firing frequency is increased

• increased burst frequency

• higher interspike intervals between bursts, lower percent of time cells are firing at greater than 10 Hz

• retinal waves not regulated by nicotinic acetylcholine receptors as is true for controls

• beta-glycerrhetinic acid (gap junction blocker) decreases wave frequency in mutants but not in controls

Genotype
MGI:2663180

hm2

• Allelic Composition: Chrnb2^tm1Mdb/Chrnb2^tm1Mdb
• Genetic Background: involves: 129S7/SvEvBrd * C57BL/6J

normal phenotype

no abnormal phenotype detected ( J:73590 )

• mice are viable and fertile and grow normally, with no obvious physical or neurological abnormalitites

Genotype
MGI:2663179

cx3

• Allelic Composition: Chrnb2^tm1Mdb/Chrnb2^tm1Mdb; Chrnb4^tm1Mdb/Chrnb4^tm1Mdb
• Genetic Background: involves: 129S7/SvEvBrd * C57BL/6J

mortality/aging

postnatal lethality, complete penetrance ( J:73590 )

• most homozygous animals die within 10 days of birth and the remainder die by 3 weeks of age

growth/size/body

delayed ear emergence ( J:73590 )

• delayed opening and flattening of the ears after birth

postnatal growth retardation ( J:73590 )

• growth is significantly impaired compared to controls

homeostasis/metabolism

homeostasis/metabolism phenotype ( J:73590 )

N • blood chemistry measurments for glucose, electrolytes, phosphate, calcium, magnesium, urea nitrogen, creatinine, alanine aminotransferase, aspartate aminotransferase, and bilirubin are similar to controls

N • urine chemistry measurments for glucose, electrolytes, phosphate, calcium, magnesium, and creatinine are similar to controls

immune system

urinary bladder inflammation ( J:73590 )

• inflamed urinary bladder

increased susceptibility to bacterial infection ( J:73590 )

• urine is sometimes cloudy with a dense accumulation of bacteria and white blood cells

behavior/neurological

impaired pupillary reflex ( J:73590 )

• no contraction in response to light

muscle

muscle phenotype ( J:73590 )

N • smooth muscle contraction in the urinary bladder can be induced with the muscarinic agonist CCH suggesting normal muscle function

intestinal hypoperistalsis ( J:73590 )

• reduced intestinal motility

nervous system

abnormal autonomic nervous system physiology ( J:73590 )

• profiles of current recordings from nicotine-elicited superior cervial ganglion neurons show no that nicotine does not elicit inward currents at any concentration tested, wheras robust inward currents are seen in controls

abnormal single cell response ( J:73590 )

• profiles of current recordings from nicotine-elicited superior cervial ganglion neurons show no that nicotine does not elicit inward currents at any concentration tested, wheras robust inward currents are seen in controls

renal/urinary system

abnormal urinary bladder urothelium morphology ( J:73590 )

• necrotic mucosa observed in 3 of 4 mice examined

• bladder mucosa was dysplastic with malignant characteristics in 2 of 4 mice examined

cystolithiasis ( J:73590 )

• in older animals, the bladder often contains numerous urinary stones

distended urinary bladder ( J:73590 )

• distended bladders are seen in 3 of 7 mice

abnormal urinary bladder physiology ( J:73590 , J:102601 )

• nicotine failed to elicit contraction in bladder strips whereas contraction was easily induced in controls (J:73590)

• contractile responses to nicotine in bladder strips from 2- to 5-day-old mutant mice are severely attenuated (J:102601)

urinary bladder inflammation ( J:73590 )

• inflamed urinary bladder

urinary incontinence ( J:73590 )

• wetness of the genital area is noted; chronic urinary dribbling is observed throughout life

vision/eye

impaired pupillary reflex ( J:73590 )

• no contraction in response to light

mydriasis ( J:73590 )

• widely dilated ocular pupils

narrow eye opening ( J:73590 )

• small palpebral fissures

eyelids fail to open ( J:73590 )

• eyes remain closed after postnatal day 15

craniofacial

delayed ear emergence ( J:73590 )

• delayed opening and flattening of the ears after birth

hearing/vestibular/ear

delayed ear emergence ( J:73590 )

• delayed opening and flattening of the ears after birth

digestive/alimentary system

intestinal hypoperistalsis ( J:73590 )

• reduced intestinal motility

integument

delayed hair appearance ( J:73590 )

Genotype
MGI:4822560

cx4

• Allelic Composition: Chrna7^tm1Bay/Chrna7^tm1Bay; Chrnb2^tm1Mdb/Chrnb2^tm1Mdb
• Genetic Background: involves: 129S7/SvEvBrd * C57BL/6J

behavior/neurological

behavior/neurological phenotype ( J:94667 )

N • mutant and control mice have similar rates of locomotor movement in the open field test; they also display similar levels of exploration of the "anxiety-provoking" area of the open-field indicating that both genotypes show similar anxiety-related responses

N • vertical movement, i.e. rearing behavior, is also not significantly different between mutant and control mice

N • no differences in prepulse inhibition of the acoustic startle response are detected between mutant and control mice

impaired passive avoidance behavior ( J:94667 )

• compared to controls, mutant mice show significantly decreased latencies to enter the dark side of a light/dark box in a passive avoidance test after an initial shock on the dark side; an increase in shock intensity did not alter the results significantly suggesting that mutant mice do not have a decreased sensitivity to the shock

decreased anxiety-related response ( J:94667 )

• in contrast to the open field test, mutant mice show significantly more light-dark transitions in a light/dark crossing task compared with the controls, suggesting decreased anxiety; however, the latency to enter the dark side is similar to controls

enhanced coordination ( J:94667 )

• in a rotarod test, mutant mice spend more time walking on top of the rotating rod after training than controls

hyperactivity ( J:94667 )

• authors report that mice appear hyperactive, but the result is not statistically significant