Strain Name:
Stock Number:
Citation ID:
Other Names:
Six6 Flox

Gene Information

Name: sine oculis-related homeobox 6; targeted mutation 1.1, Pamela L Mellon
Synonyms: Six6flox
Type: Allele
Species: Mus musculus (mouse)
Chromosome: 12
Alteration at locus: Conditional
Name: sine oculis-related homeobox 6
Synonyms: Six9, Optx2
Type: Gene
Species: Mus musculus (mouse)
Chromosome: 12
Alteration at locus: Conditional
NCBI: 20476
Homologene: 7220
Genetic Alterations

Six6flox mice were generated from a Six6 European Conditional Mouse Mutagenesis Program(EUCOMM) KO first construct. Because the Six6 gene has only two exons and thus only one intron, an artificial intron was inserted into exon 1 to contain the flippase recombinase target(FRT)–flanked selection cassette followed by the 5' loxPsite. The intron was derived from the Ifitm2 gene and remains in the final Six6 exon 1 in the floxed mouse, where it contains the remaining single FRT element and the 5' loxP site. The plasmid was introduced by electroporation into male C57BL/6J mouse embryonic stem cells, selected by using G418 (selection against vector insertion was diphtheria toxin A on the backbone of the plasmid), and screened for homologously recombined cells by PCR. A homologously recombined clone of mouse embryonic C57BL/6J stem cells was then injected into albino C57BL/6J blastocysts to produce chimeric mice. These were screened for percentage chimerism and correct recombination. The highest percentage male chimeric mice were bred to C57BL/6J females to create heterozygous Six6flox mice. Once confirmed as correctly floxed for Six6, they were crossed with a FLPase mouse (B6;SJL-Tg(ACTFLPe)9205Dym/J - RRID:IMSR_JAX:003800) to remove the selection cassette, leaving only one FRT site and the 5' loxP site in the artificial intron and the 3' loxP site in the original intron between exons 1 and 2 to create the Six6flox conditional KO allele. LoxP sites flanked most of exon 1 of the Six6 gene. Floxed homozygous mice evidenced no previously described phenotypes, indicating that the artificial intron was correctly spliced.

ES Cell Line
Not specified
No phenotype unless crossed with a Cre allele.

Conditional phenotype: Yes, various when crossed with specific Cre alleles.

MeSH Terms
  • Animals
  • Apoptosis
  • Gonadotropin-Releasing Hormone/genetics
  • Homeodomain Proteins/physiology
  • Hypogonadism/etiology
  • Infertility/etiology
  • Male
  • Mice, Inbred C57BL
  • Trans-Activators/physiology
  • Circadian Rhythm/physiology
  • Gene Expression Regulation/physiology
  • Gonadotropin-Releasing Hormone/metabolism
  • Homeodomain Proteins/metabolism
  • Hypothalamus/metabolism
  • Mice
  • Neurons/metabolism
  • Neuropeptides/metabolism
  • Suprachiasmatic Nucleus/growth & development
  • Suprachiasmatic Nucleus/physiology
  • Trans-Activators/metabolism
  • Transcription Factors/metabolism
Strain Development
See details in the "Genetic Alterations" section. The mice were backcrossed for many years to C57BL/6NHsd.
Suggested Control Mice
  • Developmental Biology
  • Neurobiology
  • Reproduction
Pamela Mellon, Ph.D., University of California, San Diego.
Primary Reference

Pandolfi EC, Tonsfeldt KJ, Hoffmann HM, Mellon PL. Deletion of the Homeodomain Protein Six6 From GnRH Neurons Decreases GnRH Gene Expression, Resulting in Infertility. Endocrinology. 2019 Sep 1;160(9):2151-2164. doi: 10.1210/en.2019-00113. (Medline PMID: 31211355)

Pandolfi EC, Breuer JA, Nguyen Huu VA, Talluri T, Nguyen D, Lee JS, Hu R, Bharti K, Skowronska-Krawczyk D, Gorman MR, Mellon PL, Hoffmann HM. The Homeodomain Transcription Factors Vax1 and Six6 Are Required for SCN Development and Function. Mol Neurobiol. 2020 Feb;57(2):1217-1232. doi: 10.1007/s12035-019-01781-9. Epub 2019 Nov 9. (Medline PMID: 31705443)

Colony and Husbandry Information

Colony Surveillance Program and Current Health Reports

For more information about this colony's health status contact
Coat Color
MMRRC Breeding System
N5+ (C57BL/6NHsd)
Overall Breeding Performance
Viability and Fertility: Female Male Comments
Homozygotes are viable: Yes Yes
Homozygotes are fertile: Yes Yes
Heterozygotes are fertile: Yes Yes
Age Reproductive Decline: 7 to 9 months 10 to 12 months
Average litter size
7 to 9
Recommended wean age
3 Weeks
Average Pups Weaned
7 to 9

Order Request Information

When this strain becomes available, 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.

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A Commercial License Agreement from the Donor is required for for-profit entities to use this strain. For more information, please contact Devora Rossi

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