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Strain Detail Sheet

Published: 11/30/2023
Revised: 08/24/2026

Strain Name:
B6J.129X1(Cg)-Ntrk2tm1Lfr/Mmjax
Stock Number:
065436-JAX
Citation ID:
RRID:MMRRC_065436-JAX
Other Names:
Ntrk2tm1Lfr/Mmucd (000187-UCD)

Strain Information

Gene Details

Ntrk2tm1Lfr
Name: neurotrophic tyrosine kinase, receptor, type 2; targeted mutation 1, Louis F Reichardt
Synonyms: trkBfbz, TrkBlox, fBZ
Type: Allele
Species: Mus musculus (mouse)
Chromosome: 13
Alteration at locus: Knockout
Ntrk2
Name: neurotrophic tyrosine kinase, receptor, type 2
Synonyms: trkB, C030027L06Rik, Tkrb
Type: Gene
Species: Mouse
Chromosome: 13
NCBI: 18212
VEGA: 13
HGNC: HGNC:8032
Homologene: 4504

Additional Resources
IMPC
Google
Entrez
PubMed
IMSR
Gene Ontology
BioGPS
Gene Cloud
IGTC
Mouse Phenome DB
Mouse Mine
KOMP Phenotyping
Monarch
GeneCards
ClinGen
Genetic Alterations
The first exon was replaced with a floxed full-length cDNA copy of the gene followed by a PGK-neo-loxP cassette and a tau-lacZ cassette. The PGK-neo-loxP cassette was removed in correctly-targeted ES cells via transient expression of Cre recombinase, leaving the floxed cDNA and tau-lacZ cassette intact. Expression of the floxed cDNA is under the control of the endogenous promoter. The tau-lacZ sequence is not transcribed due to SV40 polyadenylation signals and multiple stop codons following the floxed cDNA.
Genotype Determination
ES Cell Line
JM-1

Strain Description

Phenotype
Updated Information August 2026: The first author of the primary publication (Xu et al., 2000 J Neurosci 20:6888; PMID:10995833) confirmed that prior to Cre recombinase exposure, this fBZ conditional reporter/knock-out allele (Ntrk2tm1Lfr) is a hypomorph that has ~75% reduced full-length TrkB expression compared to endogenous amounts. Furthermore, homozygous fBZ mice exhibit lethality beginning ~3 months of age.

The fBZ conditional reporter/knock-out allele possess loxP sites flanking exon S (first coding exon) of the Ntrk2 gene and a tau-lacZ sequence. Prior to exposure to Cre recombinase, the tau-lacZ sequence is not transcribed. Northern blot analysis of brain from homozygous mutant animals shows the presence of only full-length transcripts. Multiple alternative transcripts observed in wildtype animals are absent from this allele. Gene expression and protein expression from this mutant allele is approximately 33% and 24% that of wildtype, respectively. Immunohistochemical analysis demonstrated that only full-length protein, and no protein isoforms, are expressed in mutant animals, and the pattern of expression is similar to wildtype. fBZ homozygous mice also develop a 20% reduction in retinal ganglion cells by ~3 months of age, at which time they begin to exhibit lethality.

Conditional Phenotype: Upon exposure to Cre recombinase, the loxP flanked Ntrk2 cDNA is deleted, resulting in an Ntrk2 null allele (and expressing the tau-lacZ reporter). This strain may be useful for studying neurobiology such as synaptic plasticity in the hippocampus.
Mammalian Phenotype Terms
Allelic Composition: Ntrk2tm1Lfr/Ntrk2tm1Lfr (Genetic Background: involves: 129X1/SvJ )
Allelic Composition: Ntrk2tm1Lfr/Ntrk2+ (Genetic Background: involves: 129X1/SvJ )
MeSH Terms
  • Animals
  • Antigens, Differentiation/metabolism
  • Axons/metabolism
  • Brain-Derived Neurotrophic Factor/metabolism
  • Calcium-Calmodulin-Dependent Protein Kinase Type 2
  • Calcium-Calmodulin-Dependent Protein Kinases/genetics
  • Hippocampus/cytology
  • Hippocampus/metabolism
  • In Vitro Techniques
  • Long-Term Potentiation/genetics
  • Mice
  • Mice, Inbred C57BL
  • Mice, Transgenic
  • Neuronal Plasticity/genetics
  • Patch-Clamp Techniques
  • Presynaptic Terminals/metabolism
  • Pyramidal Cells/metabolism
  • RNA, Messenger/biosynthesis
  • Receptor, Nerve Growth Factor/antagonists & inhibitors
  • Receptor, Nerve Growth Factor/metabolism
  • Receptor, trkB/deficiency
  • Receptor, trkB/genetics
  • Receptor, trkB/metabolism
  • Receptors, Glutamate/metabolism
  • Signal Transduction/genetics
  • Stem Cells
Strain GQC Summary
Gene Specific Genotyping:

To request gene-specific and other genotyping services for a strain, please contact the distribution MMRRC Center for more information.

Background Genetic Quality:

The MMRRC has developed a Genetic Quality Control pipeline using the MiniMUGA array to provide additional information to identify and validate genetic backgrounds of MMRRC strains. For more information on whether genetic background data is available, please contact MMRRC_GeneticQC@med.unc.edu. Note: that MiniMUGA genetic background data is not available on all strains, but can be ordered if desired.

Suggested Control Mice
Littermates of all relevant genotypes.

Research Applications

  • Models for Human Disease
  • Neurobiology

Strain Origin

Submitter
Russ Ferland, Ph.D., Albany Medical College.
Louis Reichardt, Ph.D., University of California, San Francisco.
Primary Reference
Xu B, Gottschalk W, Chow A, Wilson RI, Schnell E, Zang K, Wang D, Nicoll RA, Lu B, Reichardt LF. The role of brain-derived neurotrophic factor receptors in the mature hippocampus: modulation of long-term potentiation through a presynaptic mechanism involving TrkB. J Neurosci. 2000 Sep 15;20(18):6888-97. doi: 10.1523/JNEUROSCI.20-18-06888.2000. PMID: 10995833; PMCID: PMC2711895.
Strain Development
  1. Targeting in JM-1 embryonic stem cells (129X1/SvJ) followed by 10 backcrosses to C57BL/6NCrl.
  2. B6N.129X1-Ntrk2tm1Lfr/Mmucd crossed to C57BL/6J (N3) produced STOCK Ntrk2tm1Lfr/Mmucd (alternate name: B6.129X1-Ntrk2tm1Lfr/Mmucd)
  3. STOCK Ntrk2tm1Lfr/Mmucd Cre'ed with B6J(Cg)-Tg(Nr5a1-cre)7Lowl/J for 7+ generations produced B6J.129X1(Cg)-Ntrk2tm1.1Lfr/Mm**
  4. Four backcrosses to C57BL/6J to breed out Cre allele for MMRRC archiving. Since the Cre allele was never expressed in reproductive tissues, the offspring carries the tm1 allele.

Disclaimer: If MMRRC Strain Genetic Quality Control (GQC; based on MiniMUGA genotyping and analysis) has been completed for this strain, the information might differ from the genetic background information provided by the submitter. MiniMUGA genetic analysis is done on a strain's tissue samples taken when archived by or ordered from the assigned MMRRC Center.

Colony and Husbandry Information

Health Status Report

Cryo-recovered strains distributed by the MMRRC at JAX are shipped to the customer from the Pathogen & Opportunistic-Free Animal Room G200 - see https://www.jax.org/jax-mice-and-services/customer-support/customer-service/animal-health/health-status-reports.

Mice recovered from a cryo-archive will have health surveillance performed on recipient females. Health reports will be provided prior to shipment. If you require additional health status information, please email csmmrrc@jax.org.

Appearance

Coat Color
Black
Eye
Black

Breeding

MMRRC Breeding System
Backcross
Generation
N10+ (C57BL6/J)
Overall Breeding Performance
Good

Reproductive Statistics

Viability and Fertility: Female Male Comments
Homozygotes are viable: No No The floxed allele (prior to Cre-recombination) is a hypomorph that is homozygous lethal at ~3 months of age.
Homozygotes are fertile: Yes Yes
Heterozygotes are fertile: Yes Yes
Age Reproductive Decline: 7 to 9 months 7 to 9 months
Average litter size
7 to 9
Recommended wean age
3 Weeks
Average Pups Weaned
7 to 9

Order Information

Availability Level

Limited quantities of breeder mice (recovered litter) are available from a cryoarchive; recovered litter usually available to ship in 3 to 4 months.

Cryopreserved material may be available upon request, please inquire to csmmrrc@jax.org for more information.

Conditions of Distribution

Distribution of this strain requires submission of the MMRRC Conditions of Use (COU). A link to the COU web form will be provided via email after an order has been placed; the form should be completed then or the email forwarded to your institutional official for completion.

Fees

Additional charges may apply for any special requests. Shipping costs are in addition to the basic distribution/resuscitation fees. Information on shipping costs and any additional charges will be provided by the supplying MMRRC facility.

Click button to Request this one strain. (Use the MMRRC Catalog Search to request more than one strain.)
MMRRC Item # Description Distribution Fee / Unit (US $)
*Shipping & Handling not included*		 Units Notes
065436-JAX-SPERM Cryo-preserved spermatozoa $473.00 / $473.00
Non-Profit / For-Profit 		Aliquot Approximate quantity3
065436-JAX-RESUS Litter recovered from cryo-archive $2,187.00 / $2,187.00
Non-Profit / For-Profit 		Litter Recovered litter4; additional fees for any special requests.
Cryopreserved material may be available upon request, please inquire to csmmrrc@jax.org for more information.

1 The distribution fee covers the expense of rederiving mice from a live mouse; you will receive the resulting litter. The litter will contain at minimum one mutant carrier; the actual number of animals and the gender and genotype ratios will vary. (Typically, multiple breeder pairs can be established from the recovered litter.) Prior to shipment, the MMRRC will provide information about the animals recovered. If you anticipate or find that you need to request specific genotypes, genders or quantities of mice in excess of what is likely from a resuscitated litter, you may discuss available options and pricing with the supplying MMRRC facility.

2 An aliquot contains a sufficient number of embryos (in one or more vials or straws and based on the transfer success rate of the MMRRC facility) to transfer into one to three recipients. The MMRRC makes no guarantee concerning embryo transfer success experienced in the recipient investigator's laboratory. Neither gender nor genotype ratios are guaranteed.

3 An aliquot is one straw or vial with sufficient sperm to recover at least one litter of mice, as per provided protocols, when performed at the MMRRC facility. The MMRRC makes no guarantee concerning the success of these procedures when performed outside the MMRRC facilities.

4 The distribution fee covers the expense of resuscitating mice from the cryo-archive; you will receive the resulting litter. The litter will contain at minimum one mutant carrier; the actual number of animals and the gender and genotype ratios will vary. (Typically, multiple breeder pairs can be established from the recovered litter.) Prior to shipment, the MMRRC will provide information about the animals recovered. If you anticipate or find that you need to request specific genotypes, genders or quantities of mice in excess of what is likely from a resuscitated litter, you may discuss available options and pricing with the supplying MMRRC facility.

To request material from the MMRRC: Please fill out our on-line request form (accessible from the catalog search results page, or click the Request this Strain button in the fees section). If you have questions or need assistance completing this form, you may call Customer Service at (800) 910-2291 (in USA or Canada) or (530) 757-5710 (international calls). Before you call, please have with you: the MMRRC item number, quantity needed, Bill-to and Ship-to contact information.