Biology of cultured cells conti- Part 4 By : Saib al owini

Cell proliferation Cell cycle Cell cycle regulation differentiation

Interphase 95% of cell cycle Organelle duplication, DNA replication, and cell Growth

G1 Metabolically active Organelle duplication, but no DNA Duration variable short in embryonic, cancer cells Prepares for S phase Cells that remain in G1 for a long time = G0 (permanent tissues, such as neural tissue)

s Committed to cell division once this starts DNA and centrosome replication two identical daughter genomes

G2 Growth continues Enzymes and proteins synthesized for cell division

mitosis plus cytokinesis Mitosis: Prophase Metaphase Anaphase Telophas

Embryonic cells Cell growth not part of cell cycle All energy goes into DNA synthesis So G1 lacking and G2 quite short Each round of division subdivides cytoplasm into smaller and smaller cells, Until adult cell size is reached

Cell cycle regulation

G1 check point Cyclin D Sensitive to growth factors (rapidly degraded) Cdk –cyclin D complex drives cell through G1 to S phase

Rb Key substrate of Cdk- cyclin D complex Binds to transcription factor E2F Growth factors- activated Cdk-Cyclin Phosphorylates Rb to Allows transcription to proceed Rb gene: expresses Rb protein, acts as G1 brake

G2 check Function of G2 checkpoint: error check: DNA replication must be completed Detects unreplicated DNA, holds cell at G2 Detects damaged DNA, arrests cell in G2 until damage repaired

Mitotic Cdk-Cyclin Complex (MPF) and G2 Mpf Controls G2 checkpoint by phosphorylating proteins involved in early stages of mitosis

Regulation at Spindle Assembly Checkpoint Check for chromosome attachment to spindle MPF causes activation of anaphas- promoting complex Complex pathway that promotes anaphase

p53: Tumor Suppressor gene DNA damage increased levels of p53 p53 is a transcription factor activates gene coding for p21 P21: P21: cdk inhibitor that arrests cells in G1 until damage repaired If DNA repair not successful, p53 induces apoptosis apoptosis Called guardian of the genome 50% of all cancers related to mutations of p53

control of proliferation Cells density ( EGF,PDGF,FGF) Contact inhibition +VE OR NEGATIVE

Differentiation Maintenance : * interaction - collagen gell -cellulose -matrix glycoprotein * soluble inducer ( hydrocortisone, retinoides) Without serum

Dedifferentiation, deadaptaion Proliferation (or ) differentiation

How to prepare suitable condition for 1ry culture Ph Buffers