Strain Name:
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Gene Information

Name: sideroflexin 1; mutation 1, Mark Fleming
Synonyms: f
Type: Allele
Species: Mus musculus (mouse)
Chromosome: 13
Alteration at locus: Spontaneous Mutation
Name: sideroflexin 1
Synonyms: 2810002O05Rik, A930015P12Rik
Type: Gene
Species: Mus musculus (mouse)
Chromosome: 13
Alteration at locus: Spontaneous Mutation
NCBI: 14057
VEGA: 13
Homologene: 41494
Genetic Alterations
This is a spontaneous mutation that maps to Chr 13 consisting of a +1A insertion in the coding region of Sfxn1.
Genotype Determination

Homozygous: flexed tail homozygotes can be identified hematologically as early as embryonic day 13 and are detectably paler than normal by embryonic day 16, with most paler than normal by embryonic day 15. Homozygotes are small at birth and have a transitory siderocytic hypochromic anemia due to defective heme synthesis in fetal but not adult reticulocytes. Fetal erythrocytes have more alpha hemoglobin synthesis than beta hemoglobin synthesis. Very high numbers of siderocytes are found at birth and this decreases during the first few weeks of life and stabilizes at approximately 3 weeks of age with 3% siderocytes, significantly higher than in wild-type adults. Most homozygotes have a belly spot and 1 to 5 flexures in the tail due to vertebral fusions. Vertebral fusions are also found elsewhere in the vertebral column. Fewer than expected homozygotes are generated indicating prenatal death and the postnatal death rate is approximately 4 times normal. A small minority of homozygotes have been found to have embryonic neural tube defects or a dorsal enlargement of the head.
Heterozygous: no observed phenotype

MeSH Terms
  • Amino Acid Sequence
  • Animals
  • Blotting, Northern
  • Blotting, Western
  • Bone and Bones/abnormalities
  • Cation Transport Proteins
  • Cell Line
  • Cell Membrane/metabolism
  • Cloning, Molecular
  • DNA Mutational Analysis
  • DNA, Complementary/metabolism
  • Frameshift Mutation
  • Humans
  • Membrane Proteins/biosynthesis
  • Membrane Proteins/genetics
  • Mice
  • Mice, Inbred BALB C
  • Mice, Inbred C57BL
  • Mice, Mutant Strains
  • Mitochondria/metabolism
  • Models, Genetic
  • Molecular Sequence Data
  • Open Reading Frames
  • Phenotype
  • Physical Chromosome Mapping
  • Sequence Homology, Amino Acid
  • Tissue Distribution
  • Base Sequence
  • Chromosome Mapping
  • DNA Primers
  • DNA Repair
  • Gene Amplification
  • Introns
  • Mutation
  • RNA Splicing/genetics
  • Smad5 Protein/genetics
Strain Development
Spontaneous mutation with transient post natal anemia and tail kinks. Maps to Chrom 13, where we found a +1A insertion in the coding region of Sfxn1. Mouse was backcrossed, intercrossed to 129S6 to generation N19.
Suggested Control Mice
Wild-type littermates or 129S6/SvEvTac
  • Cell Biology
  • Developmental Biology
  • Hematology
  • Metabolism
Mark Fleming, M.D., D.Phil., Boston Children's Hospital
Primary Reference

Kamenoff RJ Effects of the flexed-tailed gene on the development of the house mouse. J Morphol 1935 58 117-155

Fleming MD, Campagna DR, Haslett JN, Trenor CC 3rd, Andrews NC. A mutation in a mitochondrial transmembrane protein is responsible for the pleiotropic hematological and skeletal phenotype of flexed-tail (f/f) mice. Genes Dev. 2001 Mar 15;15(6):652-7. (Medline PMID: 11274051).

Hegde S, Lenox LE, Lariviere A, Porayette P, Perry JM, Yon M, Paulson RF. An intronic sequence mutated in flexed-tail mice regulates splicing of Smad5. Mamm Genome. 2007 Dec;18(12):852-60. Epub 2007 Nov 30. (Medline PMID: 18060457).

Colony and Husbandry Information

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 .
Coat Color

(see phenotype description above)

MMRRC Breeding System
Breeding Scheme(s)

Backcross/intercross scheme. Homozygous mutants are backcrossed to 129S6 to generate the next (N) obligate hets, then intercrossed to create Sfxn1-/Sfxn1- N(x)F1's.

Overall Breeding Performance
Viability and Fertility: Female Male Comments
Homozygotes are viable: Reduced Reduced
Homozygotes are fertile: Yes Yes
Heterozygotes are fertile: Yes Yes
Age Reproductive Decline: 6 months 12 months
Recommended wean age
3 weeks

Order Request Information

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 for more information.

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.

The donor or their institution limits the distribution to non-profit institutions only.

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 $) Units Notes
036656-JAX-SPERM Cryo-preserved spermatozoa $437.00 / Non-Profit Aliquot Approximate quantity2
036656-JAX-RESUS Litter recovered from cryo-archive $2,022.00 / Non-Profit Litter Recovered litter1; additional fees for any special requests.
Cryopreserved material may be available upon request, please inquire to for more information.

1 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.

2 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.

3 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.

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.