Algorithmic and combinatorial studies inspired by problems of comparative genomics

我的研究兴趣是开发算法方法和组合工具，以解决比较基因组学领域出现的生物学问题所启发的理论问题。比较基因组学的基本目的之一是从不同物种的基因组比较中提取信息。这些信息涉及基因组序列本身，基因在不同基因组中出现的顺序，小分子（如RNA）的结构等。从大量生物信息中提取有意义的信息的一般问题引起了许多重要的理论问题，如单词，排列，树或图形的精细组合。我的研究计划的第一部分涉及研究和比较代表非编码RNA（ncRNA）结构的特殊树和图。这项研究对生物学特别重要，因为ncRNA的重要细胞功能取决于它们的结构和组合特性。此外，ncRNA结构的复杂数据库的快速扩展（从2002年的仅3个已知家族到今天的1,400多个）保证了更快的算法的发展，用于比较和分析这些结构。第二部分涉及研究排列或有符号排列，这些排列表示不同基因组中基因的出现顺序。在这里，问题在于找到距离d下的一组排列的中值，并且受到比较基因组学的基因顺序问题的启发，其中不同物种基因组中基因出现顺序的差异被用来评估它们之间的进化距离。最后，在生物信息学领域开发更有效的比较算法所产生的预期理论结果必将有助于解决计算机科学其他领域的类似问题。我们已经展示了我们的结果如何可以应用在软件工程的背景下，系统的维护需要在程序代码中搜索经常性的图案。

My research interests are in developing algorithmic approaches and combinatorial tools to solve theoretical problems inspired by biological problems arising in the field of comparative genomics. One of the basic aim of comparative genomics is to extract information from the comparison of genomes of different species. This information concerns the genomic sequence themselves, the order of appearance of genes in different genomes, the structure of small molecules (like RNA), etc. The general problem of extracting meaningful information from the resulting mass of biological information gives rise to many important theoretical problems on the fine combinatorics of words, permutations, trees or graphs. A first portion of my research program concerns the study and comparison of special trees and graphs representing non-coding RNA (ncRNA) structures. This study is of particular importance for biology because important cellular functions of ncRNA depend on their structural and combinatorial properties. Moreover, the fast expansion of complex databases of ncRNA structures (from barely 3 known families in 2002, to over 1,400 today) warrants the development of faster algorithms for the comparison and the analysis of such structures. A second portion concerns the study of permutations or signed permutations representing the order of appearance of genes in different genomes. Here, the problem consists in finding the median of a set of permutations under a distance d and is inspired by the gene order problem of comparative genomics, where the difference in order of appearance of genes in the genome of different species is used to evaluate the evolutionary distances between them. Finally, the expected theoretical results that will arise from the development of more efficient comparison algorithms in the field of bioinformatics is bound to help to solve similar problems in other field of computer science. We have already shown how our results may be applied in the context of software engineering where the maintenance of system requires the search of recurrent motifs in a program code.