Problem 4

A341 Stem Cell and Tissue Engineering

Problem 4 : More than Cells!6th Presentation

Activity Owner : Dr Alvin Teo Inputs: Dr Ng Hian Cheong Modified by Dr Kam Boon Horng Approved By : Ms Song Sin Nee Module Chair : Dr Leong Wen Shing

Copyright 2011 Republic Polytechnic, Singapore

The problem Examine what make cells different from one another through their protein content. Investigate into the processes for a single cell (zygote) to give rise to a functional tissue or organ and understand the mechanisms involved.Copyright 2011 Republic Polytechnic, Singapore

What can you recognize & infer? Cells in the adult body looks different from the fertilized egg cell, and have specific functions Up to 250 cell types But they all have the same genome (there are special exceptions) DNA Unique biomolecule transmitted from sperm/egg to progeny cells Stable Double-stranded polymers made up of 4 basic units Contain information in its sequence Half of the progenys DNA originated from mother egg cell; the other half from fathers spermatozoan Act as template for its own replication ---------DNA replication


An Approach What make cells different? Why is there different protein profiles in cells? How did one cell give rise to itself and a different cell? How do cells communicate to decide on their fate?


What make cells different? Chemical activities is the basis of cellular functions, shape and appearance. Cells are different as a result of the differences of chemical activities occurring within them. Chemical activities at any one time are determined by the enzymes, which are usually proteins Therefore, it is the different proteins that make cells differentCopyright 2011 Republic Polytechnic, Singapore

What make cells different?Cellular functions of proteins Enzymes which dictates the chemical reactions in the cells Membrane channels controlling the flow of molecules into and out of cells Structural proteins dictating the shape of cells. and etc. But, how does the different protein profile arise?Copyright 2011 Republic Polytechnic, Singapore

Enzymes

Protein Channels

Structural Proteins

Why is there different protein profiles in cells Thecentral dogmaThe Central DogmaDNA: encoded humans genome; Transcription: copy a particular portion of DNA nucleotide sequence, i.e. a gene, into an RNA nucleotide sequence tRNA: bring amino-acids to ribosomes during protein synthesis mRNA: templates for making proteins rRNA: form part of ribosomes Ribosome: An organelle serve as the site for protein synthesis Translation: conversion of the information in RNA into protein Proteins: Execute nearly all cells function (in the form of enzymes, membrane channels, structural proteins)Copyright 2011 Republic Polytechnic, Singapore

Why is there different protein profiles in cellsRationale #1The Central Dogma

Differential gene expression

Certain part of DNA are used to make RNA during transcription differential gene expression Whole sequence of mRNA will be used for the synthesis of proteins during translationCopyright 2011 Republic Polytechnic, Singapore

Why is there different protein profiles in cellsRationale #2Different efficiencies of expressed genes

Gene A is transcribed and translated much more efficiently than gene B. This allows the amount of protein A in the cell to be much greater than that of protein BCopyright 2011 Republic Polytechnic, Singapore

How did one cell give rise to itself and a different cell? (Cell division)

A cell reproduces by duplicates its contents and then divides into two: cell division Cell division can be classified as symmetric cell division or asymmetric cell division Symmetric cell division produce two identical daughter cells Asymmetric cell division produces two daughter cells, one of which is identical to its parent cell, while the other is different from its parent cell

http://www.daviddarling.info/encyclopedia/C/cell_division.html Copyright 2011 Republic Polytechnic, Singapore

How did one cell give rise to itself and a different cell?(How do cells also become different?)

A different cell produced generally depends on changes in gene expression (subsequently, profile of proteins) rather than on any changes in nucleotide sequence of the cells genome eg. Stem cell Symmetric and Asymmetric cell division


How did one cell give rise to itself and a different cell?(Stem cell)

http://www.ncbi.nlm.nih.gov/books/bv.fcgi?highlight=cell%20 division&rid=mboc4.figgrp.4095


How did one cell give rise to itself and a different cell?(Eg.1: Totipotent zygote)Embryonic Germ Layers From Which Differentiated Tissues Develop [1] Embryonic Germ Layer Differentiated Tissue

Endoderm

Embryonic stem cell (ESC)

Thymus Thyroid, parathyroid glands Larynx, trachea, lung Urinary bladder, vagina, urethra Gastrointestinal (GI) organs (liver, pancreas) Lining of the GI tract Lining of the respiratory tract

Mesoderm

Bone marrow (blood) Adrenal cortex Lymphatic tissue Skeletal, smooth, and cardiac muscle Connective tissues (including bone, cartilage) Urogenital system Heart and blood vessels (vascular system) Skin Neural tissue (neuroectoderm) Adrenal medulla Pituitary gland Connective tissue of the head and face Eyes, ears

Ectoderm


How did one cell give rise to itself and a different cell?(Eg.2: pluripotent embryonic stem cell)How does an embryonic cell give rise to muscle tissue?(An outcome of cell fate development)

Embryonic stem cell (ESC)

To illustrate the entire process in the development of an organ and all its constituent tissue/cells from a pluripotent cell through asymmetric cell division to produce multipotent mesodermal cell followed by progenitor, and finally to the differentiated progenies


How do cells communicate to decide on their fate?Mode of communication Mechanism of communication

Inter-cellular communications as a mean to determine cell fate. This is common in the spatial pattern of developmental processes.Copyright 2011 Republic Polytechnic, Singapore

What have you learnt todayIntroduction to the processes, mechanism and coordination that enable many cell types that would give rise to a functional tissue or organ The difference between cells is contributed by the different protein profiles Identical cell progeny is a result of symmetric cell division; different cell progeny is a result of either symmetric or asymmetric cell division The central dogma of Biology and different cell fate Cell fate is determined by the intercellular communicationsCopyright 2011 Republic Polytechnic, Singapore

Problem 4

Documents

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cell division cell division

cell types

different proteins

stem cell symmetric

stem cell http

different protein profiles

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