TRANSGENIC ANIMALS. -transient transfection of cells -stable transfection of cells. - Two methods to produce transgenic animals:

Giovanna Gambarotta- Only for teaching purposes. TRANSGENIC ANIMALS -transient transfection of cells -stable transfection of cells - Two methods to produce transgenic animals: 1- DNA microinjection - random insertion 2- embryonic stem cell-mediated gene transfer - random insertion - homologous recombination (double selection) - Rosa26 locus - knock-out animals - knock-in animals - conditional knock-out (cre-lox technique, inducible systems) - genomic analysis to identify genetically modified animals

STEPS TO OBTAIN A CRE/LOX MOUSE Preparation of the construct containing specific promoter+cre injection in the pronucleus of the zygote screen mice to identify CRE-transgenic mice Verify CRE expression Preparation of the construct containing loxp-exon X-neo-TK Transfection in ES cells for homology recombination Selection and screening of the clones Injection in blastocysts Chimeric mice -> +/- floxed mice: only one allele is floxed Screen mice Cross mice to obtain -> -/- floxed mice Screen mice Cross -/- floxed mice with CRE-transgenic mouse Cross +/- floxed mice-cre to obtain homozigous mice verify KO in the specific cells CRE animals can be crossed with different floxed animals! Floxed animals can be crossed with different CRE animals! CRE expression can be obtained also by virus infection (adenovirus, lentivirus)

LoxP sequence (34-bp-long) Lox P (locus of X-over P1) is a site on the bacteriophage P1 consisting of 34 bp. The site includes an asymmetric 8 bp sequence, variable except for the middle two bases, in between two sets of palindromic, 13 bp sequences. 5 -ATAACTTCGTATA NNNTANNN TATACGAAGTTAT-3 3 -TATTGAAGCATAT NNNATNNN ATATGCTTCAATA-5 13bp 8bp 13bp Multiple variants of loxp, in particular lox2272 and loxn, have been used by researchers with the combination of different Cre actions. Cre protein (from "Causes recombination or "Cyclization recombinase") consists of 4 subunits and two domains https://www.youtube.com/watch?v=olpjiwm0g7a

Only for teaching purposes - not for reproduction or sale

Cre-recombinase-mediated multicolour reporter transgenic line for lineage tracing and clonal analysis, as a genetic strategy to mark cells with multiple fluorescent proteins. Only for teaching purposes - not for reproduction or sale

Inducible systems to regulate CRE recombinase expression or expression of a gene of interest Tet-OFF Tet-ON Virus mediated expression Inducible systems to regulate CRE recombinase activity Tamoxifen

Tet-OFF Promoter 1 Promoter 2 Promoter 2 /CRE /CRE tetracycline Transactivator factor (tta), is a hybrid transcription factor resulting from the fusion of the prokaryotic Tet Repressor, TetR, with an eukaryotic transcriptional transactivation domain. TetR confers sequence specific DNA binding and sensitivity to tetracyclines. TRE=tetracycline responsive element The response of both TetR and tta to tetracyclines is similar: binding of the antibiotic dramatically lowers their affinity to their common cognate binding sites, the teto operators.

Tet-ON Promoter 1 Promoter 2 Promoter 2 /CRE /CRE rtta differs from tta by a few point mutations within TetR. These, however, result in a complete reversal of tetracycline responsiveness of this transcription factor. rtta requires tetracyclines for binding to teto. Of note, specific tetracycline derivatives like doxycycline (Dox) or anhydrotetracycline (ATc) must be used to optimally exploit the rtta phenotype.

Doxycycline, a tetracycline derivative, is currently the most preferable effector substance for both the Tet-On and the Tet-Off System. It binds with high affinity to tta as well as to rtta and, thus, is fully effective in the Tet-Off system at concentrations as low as 1-2 ng/ml in the case of tta. In the Tet-On systems, concentrations as low as 80 ng/ml, in the case of rtta2-syn1, are effective. An excellent medical safety record and well characterized pharmacological properties like excellent tissue penetration and low toxicity in eukaryotes make Dox the effector substance of choice for most applications in tissue culture and whole organisms.

In both cases, a construct for tta or rtta expression must be prepared and inserted into the mouse. Promoter 1 Tissue specific promoter/cmv CRE CRE Promoter 1 Tissue specific promoter/cmv The Tet-Off/Tet-On system can be used to obtain inducible expression of CRE (CRE-lox technique) or inducible expression/repression of a gene with an inducible promoter (random insertion or Rosa26 homologous recombination).

Inducible systems to regulate CRE recombinase expression or expression of a gene of interest Tet-OFF Tet-ON Virus mediated expression Inducible systems to regulate CRE recombinase activity Tamoxifen

The development of animal models of lung cancer is critical to our understanding and treatment of the human disease. Conditional mouse models provide new opportunities for testing novel chemopreventatives, therapeutics and screening methods that are not possible with cultured cell lines or xenograft models. This protocol describes how to initiate tumors in two conditional genetic models of human non-small cell lung cancer (NSCLC) using the activation of oncogenic K-ras alone or in combination with the loss of function of p53. We discuss methods for sporadic expression of Cre in the lungs through engineered adenovirus or lentivirus, and provide a detailed protocol for the administration of the virus by intranasal inhalation or intratracheal intubation. The protocol requires 1 5 min per mouse with an additional 30 45 min to set-up and allow for the recovery of mice from anesthesia. Mice may be analyzed for tumor formation and progression starting 2 3 weeks after infection.

Inducible systems to regulate CRE recombinase expression or expression of a gene of interest Tet-OFF Tet-ON Virus mediated CRE expression Inducible systems to regulate CRE recombinase activity Tamoxifen

Inducible Cre activity has been achieved by fusing Cre to a mutant form (ER ) of the estrogen receptor. Cre-ER is insensitive to the natural ligand (17β-estradiol), but functions as a specific receptor for the synthetic ligand 4-hydroxy-tamoxifen. In the absence of tamoxifen, Cre-ER is sequestered in the cytoplasm, complexed with hsp90. Binding to tamoxifen disrupts the interaction with hsp90 and permits the translocation of Cre-ER to the nucleus wherein it catalyzes loxp-specific recombination events.

TISSUE SPECIFIC & INDUCIBLE GENE SWITCHING ON

a Transgenic mouse A contains Cre recombinase capable of recognizing loxp sites, under the control of a specific tracer marker promoter (in this case Foxd1). The Cre recombinase is only expressed in cells that are positive for the marker. b Transgenic mouse B contains a signalling sequence (in this case GFP) that is driven by a ubiquitous driver sequence (Rosa26) that is normally prematurely terminated by an inserted stop codon. The stop sequence is flanked by loxp sites. c Crossbreeding mouse A and B can produce transgenic mouse C in which the tracer or marker promoter driven Cre recombinase recognizes the loxp sites flanking the stop sequence, upon which the latter is excised. This excision allows the driver sequence to complete transcription and translation of the signalling cassette, thus allowing for specific lineage tracing. d An epithelial cell not expressing FoxD1 does not have a tamoxifen-specific modified oestrogen receptor Cre recombinase (ER/Cre) fusion protein expressed at the cell membrane. Consequently, activation of the ER with tamoxifen does not occur and does not lead to fusion protein translocation to the nucleus and signal protein expression by recombining the stop sequence out of the DNA. In pericytes, however, FoxD1 driven ER/Cre fusion protein expression does occur. Subsequently, tamoxifen injection ultimately leads to permanent signal protein expression allowing for timed FOXD1 specific tracing of pericytes. Abbreviations: FOXD1, forkhead box D1; GFP, green fluorescent protein.

Tissue specific expression and inducible systems can be used to obtain inducible tissue specific death Example: Nestin is an intermediate filament protein specifically expressed by neural stem/progenitor cells in the developing nervous system and the adult brain. How can you obtain nestin expression specific inducible cell death?

THYMIDINE KINASE

THYMIDINE KINASE Administration of Ganciclovir (GCV) to mice carrying the transgene (GFAP-TK or Nestin-TK) results in death of dividing cells expressing herpes simplex virus thymidine kinase (HSV-TK). HSV-TK produces toxic metabolites that disrupt DNA synthesis and result in the death of dividing cells.

TAMOXIFEN CRE/ER RECOMBINASE DRIVEN EXPRESSION OF DTA

TAMOXIFEN CRE/ER RECOMBINASE DRIVEN EXPRESSION OF DTA In the Nestin-CreER/ NSE-DTA mouse, - Nestin-CreER drives the expression of a tamoxifen (Tam)-inducible form of Cre in NSCs - Cre-inducible diphtheria toxin fragment A (DTA) is engineered into the locus of the neuron-specific enolase (NSE) gene. - activated CreER leads to the recombination of loxp sites and removal of the STOP cassette upstream of the DTA gene, thus allowing the expression of DTA from the NSE promoter.

DOXYCICLINE INDUCED EXPRESSION OF BAX

DOXYCICLINE INDUCED EXPRESSION OF BAX In the Nestin-rtTA/TRE-Bax mice, doxycycline (Dox) activates the rtta protein, which binds to seven TetO sequences (TRE) to drive the expression of the proapoptotic protein Bax, which activates the apoptosis pathway in NSCs. Alternatively, also DTA could be used.

TRANSGENIC ANIMALS Giovanna Gambarotta- Only for teaching purposes. -transient transfection of cells -stable transfection of cells - Two methods to produce transgenic animals: 1- DNA microinjection - random insertion 2- embryonic stem cell-mediated gene transfer - random insertion - homologous recombination (double selection) - Rosa26 locus - knock-out animals - knock-in animals - conditional knock-out (cre-lox technique, inducible systems) - sirna

RNA interference Only for teaching purposes - not for reproduction or sale https://www.youtube.com/watch?v=ck-ogb1_ele

A short hairpin RNA or small hairpin RNA (shrna/hairpin Vector) is an artificial RNA molecule with a tight hairpin turn that can be used to silence target gene expression via RNA interference (RNAi). [ Expression of shrna in cells is typically accomplished by delivery of plasmids or through viral or bacterial vectors. shrna is an advantageous mediator of RNAi in that it has a relatively low rate of degradation and turnover.

Which are the controls in RNA interference experiments to verify that the phenotype observed depends on the absence of the gene which is the sirna target? sirna

sirna Only for teaching purposes - not for reproduction or sale

Example: ErbB4 is a tyrosine kinase receptor, expressed both in heart and in the central nervous system. ErbB4 knock out animals (ErbB4 -/- ) do not survive, because ErbB4 is necessary for heart development. If you want to study ErbB4 lack in neurons, which strategies can you follow to obtain animals missing ErbB4 in neurons, but expressing ErbB4 in heart?

Only for teaching purposes - not for reproduction or sale ErbB4 lox/lox X nestin-cre ErbB4 lox/- nestin-cre X ErbB4 lox/lox ErbB4 lox/lox nestin-cre

Only for teaching purposes - not for reproduction or sale ErbB4 lox/lox nestin-cre ErbB4 lox/lox nestin-cre

ErbB4 +/- x HER4 heart ErbB4 +/- HER4 heart x ErbB4 +/- ErbB4 -/- HER4 heart mice are null for the ErbB4 gene except in the heart, due to the expression of the HER4 transgene ErbB4 -/- HER4 heart

WHY MICE ARE A GOOD EXPERIMENTAL MODEL? 1-The shared sequence complexity between mice and humans is startling. Although some physiological and immunological differences exist between mice and humans, genomic sequencing has demonstrated that of ~30,000 genes in both mice and humans only 300 (i.e., 1%) are unique to either species. 2- All mice in a given study are generally on the same genetic background (i.e., mouse models are either in a single inbred strain or they are backcrossed on to a genetic background as to be congenic for a given strain). As a consequence, all subjects are genetically identical, eliminating potential complicating factors such as genetic variation and unique gene polymorphisms. 3-The inter-generational interval of mice is less than three months. Litter sizes are also large enough to permit the rapid expansion of experimental subjects into statistically relevant cohorts. 4-Mice in a given study have defined medical histories and all animals will be equivalently housed, experiencing identical environmental exposures. 5-All mice in a given study are subject to identical experimental protocols and it is possible for all subjects to undergo a complete assessment of endpoint pathologies, including measures of physiological parameters and post-mortem histopathology.