This web page was produced as an assignment for Genetics 677, an Undergraduate course at UW-Madison
The following is a review of a scientific article publish in The American Society of Human Genetics in 1994 about differential allelic espression of a Fibrillin gene (FBN1) in patients with Marfan Syndrome.
As already known prior to the publication of the article, Marfan Syndrome is an autosomal dominant genetic disorder that affects connective tissue. This results in abnormal phenotypes that present themselves in the cardiovascula, skeletal and ocular systems in the body. Years prior to this study the Marfan locus has been already identified as the FBN1 gene on chromosome 15, which codes for an extra-cellular matrix protein called fibrillin. Other research had reported various mutations in the gene, but all mutations were detected as changes in a cDNA copy of the fibrillin mRNA from the mutant allele. This meant that all mutations were detected in the exons of the FBN1 gene, the portion of the gene that was expressed. However, these mutations did not account for a significant amount of Marfan Syndrome patients. As stated in the article, if an individual had a mutant allele that produced unstable or no fibrillin mRNA, it would go undetected since the cDNA would only represent mRNA from the normal allele. The purpose of this study was to test heterozygosity for a polymorphism in a transcribed region of the fibrillin gene in order to distinguish the contribution of each allele to the fibrillin mRNA pool. This was accomplished by using a RsaI RFLP in the 3’UTR to look for differential allelic expression.
The techniques used in this study to test heterozygosity included PCR and allele-specific oligonucleotide hybridization using RSA(-) and RSA(+) probes. These results were expressed in several figrues. Figure 1 is a generated diagram of the FBN1 gene showing the RsaI polymorphic site that was studied. This figure was not very informative, as it does not give much information about the areas surrounding the restriction site. This could be due to the fact that not much was known about the region at the time of publication. Figure 2 is picture of a gel showing patient DNA that was digested with RsaI. Some of the data is poorly explained, as it is not clear which patients match up with each lane on the gel. This made information presented by the gel difficult to interpret. Figure 3 showed the hybridization of radioactively labeled allele-specific oligonucleotides to cDNA as well as genomic DNA to account for the mRNA detected from each allele. As the paper stated, there was a limitation to the sensitivity of the technique. The last figure, Figure 4, was a pedigree of two the individuals in the study, showing how they were related and other affected family members.
Overall, I felt this article was informative on a broad scale. The researchers explained their methods concisely and stressed the importance of the null allele in the discussion section. A good direction was given as to where further research should be focused. Although the overall message was clear, some of the details in the article were difficult to follow. Figures were poorly explained and it was difficult to match patient data to the data in the figures. Also, the article only gave details of three of the patients studied, yet it was not stated why these patients were significant over other patients involved in the study.
As already known prior to the publication of the article, Marfan Syndrome is an autosomal dominant genetic disorder that affects connective tissue. This results in abnormal phenotypes that present themselves in the cardiovascula, skeletal and ocular systems in the body. Years prior to this study the Marfan locus has been already identified as the FBN1 gene on chromosome 15, which codes for an extra-cellular matrix protein called fibrillin. Other research had reported various mutations in the gene, but all mutations were detected as changes in a cDNA copy of the fibrillin mRNA from the mutant allele. This meant that all mutations were detected in the exons of the FBN1 gene, the portion of the gene that was expressed. However, these mutations did not account for a significant amount of Marfan Syndrome patients. As stated in the article, if an individual had a mutant allele that produced unstable or no fibrillin mRNA, it would go undetected since the cDNA would only represent mRNA from the normal allele. The purpose of this study was to test heterozygosity for a polymorphism in a transcribed region of the fibrillin gene in order to distinguish the contribution of each allele to the fibrillin mRNA pool. This was accomplished by using a RsaI RFLP in the 3’UTR to look for differential allelic expression.
The techniques used in this study to test heterozygosity included PCR and allele-specific oligonucleotide hybridization using RSA(-) and RSA(+) probes. These results were expressed in several figrues. Figure 1 is a generated diagram of the FBN1 gene showing the RsaI polymorphic site that was studied. This figure was not very informative, as it does not give much information about the areas surrounding the restriction site. This could be due to the fact that not much was known about the region at the time of publication. Figure 2 is picture of a gel showing patient DNA that was digested with RsaI. Some of the data is poorly explained, as it is not clear which patients match up with each lane on the gel. This made information presented by the gel difficult to interpret. Figure 3 showed the hybridization of radioactively labeled allele-specific oligonucleotides to cDNA as well as genomic DNA to account for the mRNA detected from each allele. As the paper stated, there was a limitation to the sensitivity of the technique. The last figure, Figure 4, was a pedigree of two the individuals in the study, showing how they were related and other affected family members.
Overall, I felt this article was informative on a broad scale. The researchers explained their methods concisely and stressed the importance of the null allele in the discussion section. A good direction was given as to where further research should be focused. Although the overall message was clear, some of the details in the article were difficult to follow. Figures were poorly explained and it was difficult to match patient data to the data in the figures. Also, the article only gave details of three of the patients studied, yet it was not stated why these patients were significant over other patients involved in the study.
The above article can be found here.
References
- D. Hewett, J. Lynch, A. Child, H. Firth, & B. Sykes. (1994). Differential allelic expression of a fibrillin gene (FBN1) in patients with marfan syndrome. The American Journal of Human Genetics, 55(3), 447.
Gabrielle Waclawik
[email protected]
February 23, 2010
www.gen677.weebly.com
[email protected]
February 23, 2010
www.gen677.weebly.com
