A REPORT ON THE STUDY TITLED POSTERIOR AMORPHOUS CORNEAL DYSTROPHY IS
AREPORT ON THE STUDY TITLED:POSTERIOR AMORPHOUS CORNEAL DYSTROPHY IS ASSOCIATED WITH A DELETIONOF SMALL LEUCINE-RICH PROTEOGLYCANS ON CHROMOSOME 12
Definitionof the problem, core issues and appreciation of breadth and depth ofthe study.
Thestudy describes the problem of Posterior amorphous corneal dystrophyas a rare, autosomal dominant disorder. It is characterized bypartial or complete posterior lamellar corneal opacification,decreased corneal thickness, and flattening of the corneal curvatureamong the affected individuals. The study continues to describe thefactors occurrence this problem in other different forms apart fromthe severity of the corneal findings mentioned above, such asexpression of a number of other associated abnormalities of theanterior ocular segment, including peripheral cornea scleralization,iris coloboma, correctopia, atrophy of the iris, and iridocornealadhesions. The study tries establish the relationship between thedeletion of SMLP on Chromosome 12 and the problem of Posterioramorphous corneal dystrophy to the deletion of SLRPs.
Thedepth and breadth of the study is demonstrated by the description ofdescription of the methods used in sample collection, sequencing,analysis, the elaborate discussion and illustration that includerefences of studies done before, the well articulated conclusion thatis based on the findings and the statement of the study implication.
ASpecific technique used and its purpose.
Thestudy used next-generation sequencing technique (NGS). This method isalso known as second generation sequencing. It’s a method ofsequencing genomes at high speed, at low cost with a great accuracy¹.It’s used as a test for a family tree.
qPCRwas performed for 6 affected and 1unaffected individuals (all fromfamily 2) and as in Family 1, all 6 affected individuals were foundto have a heterozygous deletion. This results show an associationbetween Posterioramorphous corneal dystrophy and SLRPs deletions.
Thestudy concludes that a disruption of the expression of the keratinsulfates, resulting from a heterozygous deletion involving the smallleucine-rich proteoglycans (SLRPs), could lead to a subsequentalteration in the relative expression of the different cornealproteoglycans.
Further,as keratocan and lumican exhibit significantly higher cornealexpression than decorin and epiphycan, a relative decrease in theirexpression would be expected to disrupt the role of theglycosaminoglycans in the maintenance of corneal clarity.
Inaddition, the study did not find other mechanisms through which theidentified deletion of chromosome 12q21.33 could cause PACD, as theboundaries of the deletion are in intergenic regions, which in turnmeans that gene interruption, gene fusion and position effects wasvery unlikely to happen. The study did not identify any segregatingmutations by NGS, which made the unmasking of recessive alleles animprobable mechanism.
Tosum it all, the study concluded that PACD was associated with, andlikely caused by, haploinsufficiency of SLRPs on chromosome 12.
Implicationsof the study.
Theimplication of the deletion of the SLRP gene cluster as the geneticbasis of PACD provides additional evidence of the role of these genesin the development and maintenance of corneal clarity.
Therelations of the study to geneticclass and  how the genetic concept of this paper apply toanother biology class
Agenetic class has a lot to borrow from this paper/study, beginningfrom the techniques of sample collection, the scientific methods ofgenetic analysis and the results. The study is adds to the body ofknowledge, that SLRPs haploinsufficiency is a predisposing factor toPACD, and its forms the basis for which other genetic investigativestudies will be done.
Pareek,CS, Smoczy, R. & Tretyn, A. 2011. Sequencing technologies andgenome sequencing. J Appl Genet. Nov 52 (4): 413-35. Doi:10.1007/s13353-011-x.