News


March 2018
Our collaborative R01 got funded (Contact PI: Charlie Baer, UFL-Gainesville;
Consortium PI: Vaishali Katju, TAMU; co-I: Erik Andersen, Northwestern). Thank you NIH-NIGMS!


March 2018

Our followup study on the fitness (phenotypic) consequences of spontaneous mutation accumulation is now available as early online access in Evolution. We conducted independent fitness assays on spontaneous MA lines of C. elegans of varying population sizes under hypersaline conditions to determine if there exists a cryptic load of deleterious mutations whose effects were obscured under benign laboratory conditions. While the osmotic stress environment revealed a greater fitness decline in the N = 1 MA lines and more negative average effects of deleterious mutations affecting productivity and survivorship, the fitness of N = 10 and 100 lines remained indistinguishable from that of the ancestral control. Our results suggest that fitness decline is due to large effect mutations which are rapidly removed via selection, even in small populations (Ne = 5-50 individuals), with implications for conservation practices. Genetic stochasticity may not be as potent and immediate a threat to the persistence of small populations as other demographic and environmental stochastic factors. While we observed a significant fitness decline and increased risk of extinction in populations subjected to extreme bottlenecks of Ne = 1, we failed to find empirical support for a prediction of the mutational meltdown model that populations of less than 100 individuals (N =10 and 100 individuals in our experiment) are prone to extinction due the erosion of genetic integrity as a consequence of a buildup of a mutation load. Link here for the published article on early view.

October 2017

Meghan Brady has joined us as a Laboratory Technician having recently graduated from Gettysburg College with a B.S. in Biology and Environmental Studies. Welcome Meghan! 

August 2017

McKenna Stout has joined us as an Undergraduate Research Intern!  Welcome McKenna!   


May 2017

Our first paper stemming from whole-genome sequence analysis of our long-term C. elegans mutation accumulation lines just got published in Molecular Biology and Evolution (link).  Titled 'Mitochondrial mutation rate, spectrum and heteroplasmy in Caenorhabditis elegans spontaneous mutation accumulation lines of differing population size', our study of the mtDNA genomes of MA lines at differing population sizes allows us to investigate mitochondrial evolution under the joint influence of mutation and selection.  We find (i) evidence of pervasive heteroplasmy, (ii) propose that the low G+C content is a product of mutation bias rather than selection, and (iii) provide experimental support for the theoretical prediction that frameshift and nonsynonymous mutations are under stringent purifying selection.  The high frequency of the extent of heteroplasmy contributes to our high estimate of the mitochondrial effective population size per worm generation, namely 62. 


February 2017

Alexandra Powell has joined us an Undergraduate Research Intern!  Welcome Alexandra!   

December 2016

Joseph Dubie has officially joined us as a new Ph.D. student following a laboratory rotation with us earlier this fall semester !  Welcome Joseph! 


                                                              November 2016

Avery Caraway has joined us an Undergraduate Research Intern!  Welcome! 

A warm welcome to Matthew Jevit, a new student in the Graduate Progam in Genetics, who just joined us for a lab rotation!  

August 2016

Joseph Dubie and Sawyer Smith, new students in the Graduate Progam in Genetics have joined us for their first lab rotation.  Welcome, Joseph and Sawyer!!! 


July 2016

Dr. Tanya Singh has joined the Katju laboratory as a postdoctoral research fellow. Her Ph.D. dissertation was conducted in the laboratory of Dr. Paul Sniegowski in the Department of Biology at the University of Pennsylvania.  Dr. Singh focused on the effects of deleterious mutations in asexual populations using a combination of analytical and empiricial work and computer simulations.  Welcome Tanya! 


May 2016

Our invited review titled "Gene Copy-Number Changes in Evolution" just got published online in eLS (Encyclopedia of Life Sciences).

  

                                                                               April 2016

Adriana Marin and Emma Rodriguez joined our lab as new Undergraduate Research Interns. Welcome Adriana and Emma!


December 2015 

Our newly published research article in BMC Genomics in collaboration with the Bergthorsson (UNM) and Moerman (UBC) labs sought to investigate if copy-number variants constitute a common form of genetic change during adaptation in experimental C. elegans populations.  Lines were independently subjected to a regime of mutation accumulation leading to fitness decline followed by a subsequent phase of population expansion to enable fitness recovery under competitive conditions.  Multiple duplications and deletions rose to intermediate or high frequencies in independent populations during the population expansion regime.  Several lines of evidence suggest that these changes were adaptive: (i) copy-number changes reached high frequency or were fixed in a short time, (ii) many independent populations harbored CNVs spanning the same genes, and (iii) larger average size of CNVs in adapting populations relative to spontaneous CNVs.  In conclusion, we show that gene copy-number changes are a common class of adaptive genetic change.  Many convergent CNVs may be general adaptations to laboratory conditions. These results demonstrate the great potential borne by CNVs for evolutionary adaptation. (link to article)


August 2015 

Our research article on the structural and genomic features of gene duplicates in the human genome at or close to inception just got published in BMC Genomics.   Our analyses revealed both similarities and differences with other species, suggestive of  differences in prevailing duplication and duplication loss mechanisms across species. Human duplicates have, on average, much larger duplication spans which are more likely to capture entire ORFs leading to complete duplicates compared to higher proportions of structurally heterogeneous duplicates (partial and chimeric duplications) in Drosophila and C. elegans. The change in the genomic and structural features of human paralogs with evolutionary time demonstrate that (i) genomic context and structural similarities have important consequences for the fate of duplicate genes, and (ii) the mutational spectrum of gene duplicates and their subsequent evolutionary dynamics can vary significantly among eukaryotic species. (link to article)      


August 2015   

The Katju Laboratory relocated to the Department of Veterinary Integrative Biosciences in the College of Veterinary Medicine and Biomedical Sciences at Texas A&M University, worms in tow.  We are busy settling into our new home and looking forward to working with a vibrant campus-wide community of geneticists, ecologists and evolutionary biologists at TAMU.

2015 New Faculty Announcement in the College of Veterinary Medicine at Texas A&M University ... (link)


May 2015 

Lijing Bu successfully defended his Ph.D. dissertation comprising a comparative genomic study of the evolutionary features of young gene duplicates in human, chimpanzee and yeast.  
Congratulations 
Dr. Bu!!! 


Lucille Packard successfully defended her Master's thesis on the early evolutionary history and genomic features of gene duplicates in the Caenorhabditis briggsae genome.  Congratulations Lucy!!


January 2015  

Our research article on the fitness consequences of spontaneous mutations at varying population sizes (N = 1, 10, and 100) under benign conditions just got published in the January 2015 issue of Evolution.  Size N = 1 lines exhbited a 44% and 12% decline in productivity and survivorship, respectively, over 409 MA generations.  The average effects of deleterious mutations in N = 1 lines are estimated to be 16.4% for productivity and 11.8% for survivorship. Larger populations (N = 10 and 100) did not suffer a significant decline in fitness traits despite a lengthy and sustained regime of consecutive bottlenecks exceeding 400 generations. Together, these results suggest that fitness decline in very small populations is dominated by mutations with large deleterious effects. It is possible that the MA lines at larger  population sizes contain a load of cryptic deleterious mutations of small to moderate effects that would be revealed in more challenging environments. (link to article)



     © Vaishali Katju 2015