The following description highlights various aspects of the Human Genome Project that are thought to be connected in a series of events in influencing the cloning of the PARK2 gene.
The Human Genome Project (HGP), begun in 1990 and completed in 2003, has achieved many milestones. It has especially made a significant contribution in unravelling the mystery of genetic diseases.
HGP has permitted the usage of prokaryotic and eukaryotic expression vectors for cloning gene libraries representing one chromosome. To this end, it has employed the usage of Bacculoviruses artificial chromosomes (BACs) as cloning vectors because of its large insert size of 100 to 350 kbp. In the year 1996, it has established a Mapped BAC/PAC resource for studying gene isolation, sequencing and mapping. 100 BACs have been mapped to single bands in the mouse genome. So this strategy was being applied to the PARK2 gene cloning. In addition, 100 BACs have been mapped to single bands in the mouse genome. One of the important areas of HGP is chromosome mapping, which was achieved in September 1994. Here the goal was to augment the developing chromosome maps with markers for genes. Hence, with this information, linkage analysis was applied, and polymorphic markers were identified and employed that are located 17cM apart. These are markers D6S305 and D6S253.
Next, one important area of HGP is functional and comparative genomics.
Scientists have always preferred animals as it was believed that a homology exists between them and humans. As such, animals that mimic the functional biology of humans were employed as ‘model organisms’ for gene sequencing experiments by HGP.
As identifying all the 30,000 genes was one of the goals of HGP, the researchers might have come across many candidate genes; and this probably might have influenced the identification of the parkin gene, the PARK2 on chromosome 6.
It can also be perceived that as HGP has contributed to the knowledge of vital gene functions, research has commenced studying deletions of specific genes to know the exact consequences that might build.
Hence deletion mutations have gained research significance, and finally, the parkin gene deletion mutation was connected to the aetiology of a rare form of Parkinson’s disease (PD), known as autosomal recessive –juvenile parkinsonism (AR-JP) (Matsumine et al.,1998). This disease is also known as ‘familial PD’, is known to affect people of increased genetic predisposition below 21 years of age (Daniel Weintraub et al., 2008). Therefore, HGP seems to have controlled the detection of the PARK2 gene by promoting the knowledge of genetic databases.
Further, HGP also may have pressurized the need to understand the mitochondrial genome function. This is because the key gene, SOD -2 (mitochondrial dismutase 2), is reported to be involved in the pathogenesis of AR-JP due to its link with altered respiratory chain regulatory mechanisms (Hiroto Matsumine et al., 1997).
HGP has facilitated the sequencing of genomes of various ethnic populations (like Asian, Hispanic, African, and American etc.) with the objective of revealing better information about their resistance and susceptibility to a plethora of diseases. It could be one of the reasons that made the detection of AR-JP primarily in a Japanese family.
This would indicate that the disease may be limited to a particular ethnicity or only Japanese people may be showing a genetic predisposition to AR-JP, and this could have influenced the identification and cloning of the parkin gene, the PARK2 (Kitada et al., 1998).
HGP has further refined technologies to pinpoint molecular errors better.
Bioinformatic tools have facilitated a better understanding of sequence analysis and comparative genomics.
HGP has facilitated the development of Single nucleotide polymorphism (SNP’s). Because it was believed that SNP maps help in the easy identification of the multiple genes associated with many diseases, including some forms of mental illness so that this process would have further hastened the research of the PARK2 genetics.
Fatih Bayrakli et al. (2007) demonstrated that utilization of SNP and comparative genomic hybridization arrays would help in identifying microdeletion within the PARK2 gene in a family with autosomal recessive parkinsonism. This advancement had prompted the isolation of the PARK2 cDNA clones from a mouse with the goal of studying their expression patterns that are considered homologous to the human parkin gene. (Kitada et al.,2000). Therefore, it can be inferred that cloning experiments have achieved remarkable progress following a long journey since the beginning of HGP.
This has strengthened and directed subsequent genetic research. Next, as the parkin gene mutation was previously reported in AR-JP, it is reasonable to believe that HGP had accelerated the process of treating diseases by an approach known as gene therapy. Hence the parkin gene therapy has come to light and received wide acceptance in recent years (Mochizuki, 2007). The Hap Map project, yet another milestone of HGP, has strengthened the role of various genes in the aetiology of many diseases (Manolio, Brooks, & Collins, 2008). So, growing interest in this project could have furnished additional information on the PARK2 gene. Today, the PARK2 gene has found a unique place in the modern biomedical database. It was assigned numbers, symbols, ID’s, and location information with visual graphics. The root cause of this final destination is nothing but the HGP. Secondly, if the processes of HGP, thought to play a vital role in the identification and subsequent cloning of the PARK2 gene, are commencing in 2008, the following changes would be a possibility.
Initially, the information about DNA libraries and expression vectors would be scarce, and screening of patients suspected of developing AR-JP would have been difficult. Model organisms could not have been employed for gene sequencing experiments. As such, no deletion of functional genes or knock-out technologies would be in existence. Since mutation is involved in the pathogenesis of AR-JP, it could have remained undetected to date, and subsequent generations of an affected family would also have been at great risk. To say, the PARK2 induced AR-JP would not have been identified at all as a separate class of PD. Further, scantily available genomic information would not deter mitochondrial SOD-2 gene from inducing neuronal toxicity, and the associated prevalence rates of mortality would have been abundant. It may also lead to cross diagnosis of the symptoms believed to have a genetic connection. Tracing any ancestral link and ethnic association of the PARK2 would have been a huge problem. As such, researchers need to employ cumbersome approaches to studying large populations with the available conventional methods. The mutated PARK2 gene may undergo further changes presenting a new twist and additional burden to the molecular epidemiologists. There may be a likely development of the PARK2 induced AR-JP at a much younger age.
Finally, AR-JP would supersede other neurological disorders and compete with more dreadful conditions while transforming into an alarming global health problem.
Overall, HGP has turned earlier tedious and much-confined laboratory research into a comparatively easier job by providing strong computational biology tools. As such, the genetics of PD has gained widespread research significance. HGP has ensured better linkage analysis and the subsequent mapping of the PARK2 gene to human chromosome 6.
The PARK2 gene was described to be the candidate gene for AR-JP, with mutation playing a crucial role. Thereafter with the knowledge of model organism genome sequence.
It has facilitated the PARK2 gene isolation and cloning. It has further refined the aetiology of the PARK2-induced AR-JP by connecting the role of SOD-2 gene function of mitochondria.
HGP has dissected the relationship between ethnicity and genetic predisposition. This might possibly draw the attention of researchers to explore the demographic data of various countries with abundant cases of PD. HGP has played a vital role in recognizing the PARK2-induced AR-JP as a separate class of PD. This step has further expanded the research and helped in the trouble-free screening of patients complaining of symptoms characteristic of PD and its associated disorders. HGP is responsible for parkin gene therapy experiments aimed at treating PD. The Hap Map project emerged as another source of genetic information that has potential implications for the PARK2 gene research.
Now, sufficient literature is available in the databases about the PARK2 gene. Hence experiments designed for exploring the genetic aetiology of PD may not be having complexity.
Thinking in an odd sense, HGP commencement in 2008 would surely bring forth PARK2-induced complications that would remain undetectable and undiagnosed, thereby further elevating the problem of identification, isolation and cloning procedures.
References
Daniel Weintraub, MD; Cynthia L. Comella, MD, FAAN; and Stacy Horn, DO.(2008). Parkinson’s Disease—Part 1: Pathophysiology, Symptoms, Burden, Diagnosis, and Assessment. Am J Manag Care, 14, S40-S48.
Matsumine H, Yamamura Y, Hattori N, Kobayashi T, Kitada T, Yoritaka A, Mizuno Y (1998). A microdeletion of D6S305 in a family of autosomal recessive juvenile parkinsonism (PARK2). Genomics, 49, 143-6.
Hiroto Matsumine et al (1997). Localization of a Gene for an Autosomal Recessive Form of Juvenile Parkinsonism to Chromosome 6q25.2-27. Am. J. Hum. Genet. 60, 588-596.
Kitada T, Asakawa S, Hattori N, Matsumine H, Yamamura Y, Minoshima S, Yokochi M, Mizuno Y, Shimizu N(1998). Mutations in the parkin gene cause autosomal recessive juvenile parkinsonism. Nature, 392, 605-8.
Kitada T, Asakawa S, Minoshima S, Mizuno Y, Shimizu N.(2000). Molecular cloning, gene expression, and identification of a splicing variant of the mouse parkin gene. Mamm Genome, 11, 417-21.
Manolio TA, Brooks LD, Collins FS (2008). A Hap Map harvest of insights into the genetics of common disease. J Clin Invest, 118, 1590-605.
Shiaoching Gong, Chen Zheng Martin, L., Doughty, Kasia Losos, Nicholas Didkovsky, Uta, B., Schambra, Norma, J., Nowak, Alexandra Joyner, Gabrielle Leblanc, Mary, E., Hatten, Nathaniel Heintz.(2003). Nature 425, 917-925.
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