Hybridization

reagents:
labeled tumor and normal-DNA (see protocol Nick translation)
salmon sperm DNA, 10 mg/ml (e.g. Promega)
human Cot1 DNA, 1 mg/ml (GibcoBRL, Life Technologies)
3M sodium acetate
100% ethanol, 90% ethanol, 70% ethanol
Formamide (FA), (e.g. from Merck)
Master mix (20% dextransulfate/4xSSC)
SSC (20x)
70% FA/2xSSC for chromosome denaturation (120 µl per slide)
18x18 mm² cover slips, 60x24 mm² cover slips (e.g. Menzel)
rubber cement (Fixogum, Marabu, D-71732 Tamm)

Steps:

1. precipitate DNA and dilute in hybridization solution:

10 µl tumor-DNA (Biotin-labeled)

10 µl Normal-DNA (Digoxigenin-labeled)

30 µl human Cot1-DNA

1 µl salmon sperm-DNA

5,1 µl 3 M sodiumacetate

150 µl 100% ethanol (-20°C)

pipette all solutions mentioned above -->store at -80°C for 30 min--> centrifuge the tube for 10 min at max. speed at 4°C--> remove the supernatent--> wash the pellet with 500 µl 70% ethanol --> centrifuge for 10 min at 4°C--> remove the supernatent--> dry the pellet in the speed vac centrifuge for 5-10 min--> solve the pellet in 5 µl formamide, incubate the probe for 10 min at 37°C, add 10 µl of master mix

2. Denaturation of the genomic DNA and prehybridization

denature DNA for 5 min at 77°C, centrifuge briefly, prehybridiation at 37°C for at least 1 h

3. Inspection and denaturation of metaphase chromosomes

during the prehybridization inspect the slides with the metaphase spreads in a phasecontrast microscope, check the quality of the chromosomes and select the best region for hybridization.

add 120 µl of 70% FA/ 2xSSCto a cover slip --> place slide with chromosome spreads slowly on the drop of the denaturation solution --> turn the slide --> denature at 77°C for 90 sec in a preheated ofen --> place slide vertical to remove cover slip --> place slide in a cuvette with 70% ethanol (ice cold) --> dehydrate by placing the slides in cuvettes with an ascending concentration of ethanol (70, 90 und 100% EtOH, 2 min each) --> air dry the slides by placing the vertically

4. Addition of the hybridization solution to the slide with the metaphases

Centrifuge briefly the tube with the DNA after prehybridisation to remove vapor and fluid from the lid

--> Place slides with the denatured and dry metaphases chromosomes on a heating plate (37°C), label slides with case number --> add about 13 µl of hybridization solution --> if air bubble are present remove them by the edge of a cover slip --> cover drop with an 18x18 mm cover slip --> seal edges with rubber cement (alternatively place slides in a moist chamber without rubber cement at 37°C) --> place slides in a metall box --> place metall box in water bath at 37°C --> hybridize for 3 days

CGH