Mouse Engineering Technology Musculoskeletal Research Center 2016 Summer Educational Series David M. Ornitz Department of Developmental Biology
Core service and new technologies Mouse ES core Discussions are ongoing to determine who will provide replacement mouse ES core services and what core services will be provided. Growth and expansion of targeted ES cell lines (KOMP, EUCOMM) Transfection and colony picking for homologous recombination TALEN / CRISPR targeting in ES cells Alternatives to gene targeting in ES cells? Direct targeting in mouse oocytes with TALENs or CRISPR enhanced genomic editing Current issues with the new technologies are efficiency and offtarget effects
Where do we go from here?
Knockouts/Knockins Investigator Identify gene to target Transgenics Investigator Identify cell type to express (Cre, CreER T2, rtta, etc.) KOMP / EUCOM Repository No Yes Consultation with Core Directors Consultation with Core Directors Investigator Acquire KOMP ES clones Investigator or Transgenic Vector Core Build plasmid transgene Investigator or Transgenic Vector Core Build BAC transgene Conventional or TALEN / CRISPR targeting? Conventional TALEN / CRISPR Investigator or Transgenic Vector Core build targeting construct Transgenic Vector Core or GEIC build targeting construct Mouse ES Core Electroporation, drug selection Investigator or Core screening ES cells Mouse ES Core Karyotyping, expansion Mouse ES Core, GEIC expansion Mouse Genetics Core Microinjection - Production of chimeric mice or transgenic/targeted founders Investigator Characterize KO or transgenic lines MRC Investigator Studies Mouse Genetics Core Cryopreservation MRC Mouse Genetic Models database
Routes for Introducing Genes into Mice 1) Microinjection of DNA into zygotes (TALEN, CRISPR) 2) Injection of embryos with recombinant virus 3) Transfection of ES cells with cloned DNA, or CRISPR Selection, Characterization Chimera formation Transgenic Mice
Transgenic Mice: Gene addition Random insertion of DNA into the mouse genome Permits GOF, DN and knockdown experiments Allows gene regulatory elements to be tested Allows populations of cells to be marked with a reporter gene Occasionally allows endogenous genes to be trapped
Components of a Transgene promoter + enhancer gene coding sequence or cdna polyadenylation signal promoter cdna splice/poly A Things that are good: introns Things that are bad: plasmid sequence, lack of introns
Transgenic mouse issues: Tissue specificity ectopic expression chromosomal integration site may affect expression Temporal specificity Level of expression Insertional mutagenesis
How to make a transgenic mouse 1. Fusion Gene Construct 2. Superovulated Female Promoter ATG Coding Sequence p(a) Fertilized Eggs Microinjection 3. Germline Integration 4. DNA Analysis TRANSGENIC MOUSE 5. Breeding
http://mgc.wustl.edu/
Homologous recombination using embryonic stem cells First completely unbiased experiment of gene function in an entire mammalian organism. Discover unanticipated early embryonic roles Potential problems: Embryonic lethality Redundancy
Chimeric mouse ES cells derived from 129/SV strain, agouti coat color injected into a C57/B6 blastocyst. Mate chimeric mouse to Black mouse (C57/B6J) identify agouti offspring
Gene Knockout (conventional using ES cells) critical genetic engineering using embryonic stem cells X
Practical issues for basic gene targeting: length of homology probes to detect homologous recombination vector design Target gene Targeting vector Targeted allele
Targeted mutations gene addition Target gene Targeting vector Targeted allele random integration
Issues in interpreting targeted mutations Must be very careful to make a null allele haplotype insufficient recessive Prove that an allele is null gene expression protein expression assay for activity of protein Other types of alleles hypomorphic allele dominant negative linked random mutation - generate multiple ES lines
Issues in interpreting targeted mutations - cont. Neighboring gene effect PGK promoter - neo may influence a nearby gene remove the selection cassette to avoid this potential problem Unexpected phenotype lethal phenotype may result prior to the developmental stage of interest Targeted allele PGK-Neo
Removing the Neo selection cassette critical genetic engineering using embryonic stem cells PGK-NEO loxp loxp flox = flanked by lox X germline promoter - Cre recombinase PGK-NEO X
Conditional tissue-specific targeted mutations provides some of the best features of gene targeting and transgenic approaches may be combined with enhancer trap and gene trap experiments the targeted gene can be modified using cre and flip recombinases may be used in conjunction with inducible promoters
Regulated activation/inactivation of a gene using CreER fusion proteins critical loxp loxp flox = flanked by lox tissue specific + tamoxifen nuclear translocation promoter -CreER recombinase Cytosol critical X
EUCOMM gene targeting vector Frt SA-βgeo-PA LoxP PGK -neo Critical 5' hom ology 3' hom ology Cre Flp Frt SA-βgeo-PA LoxP Critical ogy null, reporter allele 3' conditional allele
EUCOMM gene targeting vector Frt SA-βgeo-PA LoxP PGK -neo Critical 5' hom ology 3' hom ology CreER/conditional gene targeting vector Frt SA-βgeo-PA SA-CreER-PA LoxP PGK -neo Critical 5' hom ology 3' hom ology
FGF18-eGFP:CreERT2 and loxp conditional knockout targeting vector Spe I 6486 ~ 9500 10,500 Nde I ~12,500 12,921 ~13,830 1c Spe I 15,791 ~20,800 Nde I 23,444 A INT B eng d Spe I, Nde I Swa I linearization site DTA SA- egfp- CreERT2- pa PGK- neo r - pa 1c frt loxp frt loxp loxp Short arm ~ 2-3 kb Long arm ~ 7 kb
FGF18-eGFP:CreERT2 and loxp conditional knockout targeting vector Spe I, Nde I 1a 1b SA- egfp- CreERT2- pa PGK- neo r - pa 1c 2 frt loxp frt loxp loxp Conditional allele Flp Spe I, Nde I 1a 1b 1c 2 Cre frt loxp loxp Fgf18- SA- egfp- CreERT2 targeted allele Spe I, Nde I 1a 1b SA- egfp- CreERT2- pa 2 frt loxp
Fgf18-Gfp:CreER, ROSA td Tomato endosteum Fgf18 Gfp:Cre/td tomato Control, Fgf18 wt / td tomato Tomato periosteum Fgf18 Gfp:Cre/td tomato Tomato GFP Articular cartilage Animals were given tamoxifen p5- p7 and harvested at p11. Images 3/11/14 P11
Reduced trabecular bone in Osx-Cre, Fgf18 f/f mice Control, Fgf18 f/f Osx-Cre, Fgf18 f/f Femur Femur 4 weeks 0.34 0.255 Tb. BV/TV control Osx-Cre, Fgf18 f/f 260 195 Tb. BMD 0.26 control Osx-Cre, 0.195 Fgf18 f/f Cortical BV/TV control Osx-Cre, Fgf18 f/f 240 180 Cortical BMD contr Osx-C 0.17 130 0.13 120 0.085 65 0.065 60 0 0 0 0
Reduced trabecular bone and normal osteoclast number in Osx-Cre, Fgf18 f/f mice Fgf18 f/+ control Osx-Cre, Fgf18 f/f 3 weeks
Dermo1- rtta, TetO- H2b:GFP E16 P4
Genomic Editing Shondra Miller Zinc finger nucleases (ZFNs) TAL effector nucleases (TALENs) CRISPR/Cas9 RNA-guided nuclease (RGNs) (RGNs)