In-Hyun Park et all carried out a study in which they generated induced pluripotent stem cells from patient with range of inherited disease. Thus disease specific stem cells permit reforming the normal and pathologic human tissue development in vitro which helps to examine the disease and facilitate drug development. They have generated human induce pluripotent stem cells line (iPS) in patient with a number of genetic disease such as down syndrome (DS)/ trisomy 21, shwachman-bodian-diamond syndrome (SBDS), parkinson disease (PD), gaucher disease (GD) type III, Huntington cholera, type 1 diabetes mellitus (JDM), duchenne type muscular dystrophy (DMD), backer type muscular dystrophy (BMD), lesch-nyha syndrome (LNSc), adenosine deaminase deficiency-related severe combined immunodeficiency (ADA-SCID). They have generated induced pluripotent stem cells in those diseases subsequently they could understand patterns of the disease and could identify cure for them.
The differentiation could be reversed because the development is determined by epigenetic rather than genetic events. Several studies demonstrated that somatic cells could be reprogrammed to generate induce pluripotent stem cells by injecting transcription factors which linked to pluripotency. These trans-acting factors are detected in oocyte. This finding lead to the invention of the factors that moderates reprogramming without the aid of somatic nuclear transfer (NT) because the NT is not been proved in human. There are four transcription factors (Oct4, Sox2, c-Myc, Klf4) which have been identified in the mouse. These factors said to aid in the reprogramming of mouse fibroblast to undifferentiated pluripotent stem cells. In human reprogramming the cell using these four factors would create patient specific pluripotent cell line but the expression of c-Myc cause death and differentiation of human embryonic stem cells. This recommends that arrangements of factors without c-Myc are necessary to reprogram human somatic cells. Disease specific pluripotent stem cells competent of separation into an assortment of tissues that have an effect on in every condition, thus discovery lead Park et al to investigate into particular disease to find genetic lesions so could be cured.
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These iPS cell lines help to validate the disease specific genotype which is found in the parental somatic cells. The formation of iPS cells from patient with single gene disorders permits to conduct experiment on disease phenotype in vitro which helps to repair the damage gene in the ex vivo. This gene repair process is accurate and specific for each disease therefore it's more safer way to repair gene than using other gene therapy.
Park et al findings are as follows
Down syndrome: is a genetic and metabolic disorder with three copy of chromosome 21. The extra copy of chromosome is caused by the irregular chromosome differentiation in the meiosis phase. During in vitro fertilization this chromosome abnormality could be detected in the preimplantation embryo, as a result this embryo could be used to derive hES cells.
Therefore park et al derived iPS cells from two male patients with DS and they found out that each patient had 47, XY + 21 karyotype over a number of passage.
Derived iPS cells for three diseases which are inherited as autosomal recessive disorder (as in Mendelian inheritance).
ADA-SCID: occurs due to lack of B cells, T cells and NK cells this deficiency could cause bacteria, fungi and viral infection.
ADA iPS cells were derived from the fibroblast and bone marrow mesenchymal cells found to have two allele mutations. One allele had heterozygote: a GGG to GAA transition mutation at exon 7 which caused G126R amino acid substitution. The other allele had frameshift deletion GAAGA in exon 10.
Shwachman -Bodian -Diamond syndrome: is an inherited disorder which is characterized by exocrine pancreas insufficiency, bone marrow failure, growth retardation and skeletal anomaly.
SBDS iPS cell line is also heterozygote which had point mutation in the IV2 + 2T > C intron 2 splice donor site and an IVS3 - 1G > a mutation of the SBDS gene.
Gaucher disease type III: is a lysosomal storage disease which is caused by the alteration in the acid beta-glucosidase (GBA) gene.
GD iPS cell line had 1226A > G point mutation which caused a N370S amino acid substitution and other allele had frameshift insertion of guanine at nucleotide 84 of the cDNA.
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Lesch -Nyhan syndrome: is an inherited disorder which is caused by the mutation in hypoxanthine-guanine phosphoribosyltransferase (HPRT) gene. LNS is an X linked recessive disease in which the defective gene carried by mother is transferred to her son. This disorder is characterized by self mutilating behavior and neurologic disorder. The deficiency of HPRT causes unusual build -up of uric acid in the body as results of this neurologic disorder occurs.
Park et al created an iPS cells line from female carrier which is an important finding for the study of reactivation of X chromosome throughout reprogramming.
Duchenne type Muscular Dystrophy and Backer type Muscular Dystrophy: is an inherited disorder which is typified by developing muscle weakness. DMD and BMD affect skeletal muscles that used for movements and also affect heart muscle. Both diseases may have similar symptoms but they have diverse mutation in the same gene.
Generated iPS cells line from fibroblast of patient with DMD and BMD. In the DMD iPS cell line had deletion over 45-52 exon but in BMD they could not find any deletion because it is a milder form of disease and demonstrate a larger assortment of variations.
Parkinson disease: it's a chronic disorder which generally affects the movement of muscles in the body which is managed by the brain.
Generated iPS cell line for the patient with PD but lack of understanding of genetic basis the genotype cannot be confirmed by this procedure.
Huntington disease: is an inherited disease which causes certain type of neurons in the brain to degrade. This neuronal degeneration cause uncontrolled movement or balance problems.
From the patient with HD they generated iPS cells line and found that HD is caused by a trinucleotide repeat expansion. The DNA sequence shows that normal person has 35 repeat of alleles where as the patient with HD has 72 repeats of alleles (expanded).
All of these iPS cell line generated for the variety of genetic condition demonstrated to have similar marker expression. OCT4, SOX2, NANOG, REX1, GDF3 and hTERT showed increased expression but the expression of KLF4 and c-Myc is not changed in any type of disease. DNA finger print investigation supported by PCR shows that the iPS cells lined that matches the genotype of their prenatal somatic lines which helps to exclude any transfer of infectivity in human pluripotent cells. This factor supports reprogramming of somatic cells which as a result create pluripotent stem cells line and thus pluripotent stem cells line is competent of differentiating into any type human tissue.
This procedure of generating iPS cell line restricts risk that could limit human use i.e. in the gene therapy which use virus cause expression of the cancer gene. The generation of iPS cells line would not only encourage disease research but it could also be used to avoid immune rejection in autologous cells therapy (transplantation) and facilitate gene repair during tissue reformation. iPS cell line generation in neurodegenerative disease would provide a step forward in understanding the disease however with little understanding of the genotype of the disease at present it's not possible. This could be looked into if the genetic bases would be defined in future. The generation of iPS cells is very valuable for learning the function and development of human tissue and also for the innovation of new drugs for specific diseases.
I suppose that in the upcoming years we could look forward for the advance technique that will be used for the generation of iPS cells as a result this could avoid any possible risk factors that would prevent reprogramming of human tissues. Thus advance technique will lend a hand to invent new drug treatment for the diseases that are unresolved at present. In applying the new drugs to human tissues we should be careful that drug wouldn't cause toxic as a result new and safe ways to eradicate toxicity will also developed. This new way of generating iPS cells will provide the understanding of nuclear reprogramming which possibly will help to resolve a cure for patients with a number of different diseases in the near future.