Nicholas Katsanis, Ph.D.

(Baylor College of Medicine)

Professor, Cell Biology

Our laboratory uses a multidisciplinary approach to understand the genetic and cellular basis of pleiotropic disease. Our research is driven by several key, challenging questions, including:

• What is the genetic basis of phenotypic variability in seemingly monogenic disease?

• How is it that ubiquitously expressed genes give rise to specific phenotypes?

• What is the mechanistic defect of disorders that exhibit both structural and progressive features?

• Is there a functional link between rare disorders and common traits with overlapping clinical manifestations?

To address such questions, we focused on Bardet-Biedl syndrome, a genetically and clinically heterogeneous disease characterized by retinal dystrophy, polydactyly, obesity and a constellation of neurological and behavioral abnormalities (OMIM #209900).

1.   Genetics
We and others have shown that despite a historical dichotomy between monogenic and complex traits, there exists a continuum of genetic causality, whereby mutations at a discrete number of loci cooperate to either cause the disease or modify the onset and severity of the phenotype. In BBS, for example, we have shown that three alleles at two BBS loci can cooperate to influence the penetrance and/or the expressivity of the phenotype. We have been involved in the identification of five of the known eight BBS genes in the human genome and are working to a) identify additional loci; and b) dissect their genetic interaction. In addition, we are querying whether the BBS proteins are involved in common traits that overlap with the BBS phenotype, such as childhood asthma, obesity and psychiatric illness.

2.   In vitro studies
To understand genetic interaction, we need to model it at the cellular level. To this end, we have identified a number of novel proteins that interact with the BBS proteins and are working to a) understand the nature of the BBS protein complexes; and b) determine the effect of mutations found in BBS patients on the function of such complexes. These studies are not only revealing new mechanistic insights but also helping identify new modifier genes for the BBS phenotypes.

3.   In vivo studies
Together with a network of collaborators, we are recapitulating the human BBS genotypes in several model organisms, including mouse, C. elegans, Drosophila and C. reinhardtii. We are using these models to better understand the function of the BBS proteins as well as their genetic and physical interactions. We have shown recently that the BBS phenotype is caused by defects at the cilia of different cell types, and we are now investigating the cellular and biochemical properties of such structures and their importance in tissue physiology, with particular emphasis on neuronal determination, maturation and migration.

4.   Global analysis of the ciliary proteome
To understand the function and dysfunction in our model, we need to assay the system in its totality. To that end, we have used a combination of computational genomics and bench biology to describe a large protein dataset involved in ciliary function and biogenesis. Our analyses suggest that we have identified most of the proteins required for the functionality of this organelle. We are now focusing on understanding the role of these proteins and their genetic and physical interactions by performing RNA interference coupled with microarray analysis on ciliated cells and observing the effects of loss of protein function on ciliary biology.

Email
Katsanis@cellbio.duke.edu

466 Nanaline Duke Building, Box 3709
Duke University Medical Center
Durham, NC 27710

Telephone 919-613-4694
Fax 919-684-5481

Selected Recent Publications
Khanna, et al. A common allele in RPGRIP1L is a modifier of retinal degeneration in ciliopathies. Nature Genet. 2009 May 10; 739-745.

Leitch et al. Hypomorphic mutations in syndromic encephelocoele genes MKS1 are associated with Bardet-Biedl syndrome. Nature Genet. 2008 40(4): 443-448.

Gerdes et al. Disruption of the basal body compromise proteasomal function and perturbs the intracellular Wnt response. Nature Genet. 2007 39(11): 1350-1360.

Badano JL, Teslovich TM, Katsanis N. The centrosome in human genetic disease. Nat Rev Genet. 2005 Mar;6(3):194-205.

Kulaga HM, Leitch CC, Eichers ER, Badano JL, Lesemann A, Hoskins BE, Lupski JR, Beales PL, Reed RR, Katsanis N. Loss of BBS proteins causes anosmia in humans and defects in olfactory cilia structure and function in the mouse. Nat Genet. 2004 Sep;36(9):994-8.

Fan Y, Esmail MA, Ansley SJ, Blacque OE, Boroevich K, Ross AJ, Moore SJ, Badano JL, May-Simera H, Compton DS, Green JS, Lewis RA, van Haelst MM, Parfrey PS, Baillie DL, Beales PL, Katsanis N, Davidson WS, Leroux MR. Mutations in a member of the Ras superfamily of small GTP-binding proteins causes Bardet-Biedl syndrome. Nat Genet. 2004 Sep;36(9):989-93.

Blacque OE, Reardon MJ, McCarthy J, Li C, Mahjoub MR, Ansley SL, Badano JL, Mah AK, Beales PL, Davidson WS, Johnsen RC, Audeh M, Plasterk RHA, Baille DL, Katsanis N, Quarmby LM, Wicks SR, Leroux MR. Loss of C. elegans BBS-7 and BBS-8 protein function results in cilia defects and compromised intraflagellar transport. Genes Dev. 2004 Jul 1;18(13):1630-42.

Li JB, Gerdes JM, Haycraft CJ, Fan Y, Teslovich TM, May-Simera H, Li H, Blacque OE, Li L, Leitch CC, Lewis RA, Green JS, Parfrey PS, Leroux MR, Davidson WS, Beales PL, Guay-Woodford LM, Yoder BK, Stormo GD, Katsanis N, Dutcher SK. Comparative genomics identifies a flagellar and basal body proteome that includes the BBS5 human disease gene. Cell. 2004 May 14;117(4):541-42.

Kim J-C, Badano JL, Sibold S, Esmail MA, Hill J, Hoskins BE, Leitch CC, Venner K, Ansley SJ, Ross AJ, Leroux MR, Katsanis N, Beales PL. The Bardet-Biedl protein BBS4 targets cargo to the pericentriolar region and is required for microtubule anchoring and cell cycle progression. Nat Genet. 2004 May;36(5):462-70.