A view of Jiri, Nepal

A view of Jiri, Nepal

Jiri Dental Project

As noted on the Human Craniofacial Genetics page, we began a project designed to elucidate the genetic architecture of the jaws and teeth in a population in rural Nepal.  We conducted a pilot study in this region in 2005 and received funding from the National Institute of Dental and Craniofacial Research (NIH) in 2009.  Below is a brief description of this project.  Also, please enjoy the pictures from this extremely beautiful area.  The formal title of this research is “Genetic Architecture of the Human Dentognathic Complex.”  Dentognathic refers to the teeth and jaws.  Because that can be a bit of a mouthful, we typically refer to this study as the Jiri Dental Project.

INTRODUCTION

The mouth has been the focus of more clinical specialties than any other region in the body.  Significant health problems related to the dentognathic complex range from aesthetic issues resulting from malocclusion, to the increased risk of caries due to dental crowding, to congenital deformities, such as orofacial clefting.  The etiology of dentognathic disorders is complex, with both hereditary and environmental factors contributing to the variation in these traits.  It is the diverse developmental pathways, and their interactions, that create a unique morphology in the permanent dentition and adult jaw.

STUDY GOAL

The overall goal of this study is  to conduct a genetic epidemiologic study of variation in dental and orofacial morphology in the Jirel population of eastern Nepal.  This work will be able to quantify the extent of genetic influence on dental and oral traits, the extent to which two traits share the same genetic background, and begin to localize chromosomal regions influencing dentognathic traits. 


STUDY POPULATION

The Jiri region is a geographically well-defined area of approximately 230 km2 located 190 kilometers east of Kathmandu, Nepal. The region is named for the Jirels, a Tibeto-Burman language speaking group which is the focal population for the study.  Ethnohistorical accounts and population genetic studies support the idea that the Jirels represent a hybrid population that was derived from Sherpas and Sunwars approximately 10-11 generations ago.  Since the founding event, there has been very little gene flow (< 1% per generation) into the population from either the parental or other groups.  In 1985, the Jirel population comprised approximately 3,500 individuals living in a total of nine villages. Over the past 20 years, extensive pedigree information on Jirel familial relationships has been collected. To date, approximately 2000 have also been genotyped, and all can be placed into a single pedigree that contains over 62,000 pair-wise relationships informative for genetic analysis.  This makes the Jirel pedigree the most powerful documented human pedigree currently available for study.

METHODS

To examine the genetic architecture of dentognathic traits, a Nepali dentists makes whole-mouth dental impressions of Jirel participants using a polyvinylsiloxane material typically used by dentists.  Arch width and length, as well as lengths  and widths of all available teeth are measured from dental casts using the software program designed and created by research assistant Mathew Thomas. 

ORAL HEALTH

Prior to examination, each participant provides a brief oral health history.  Of the 200 people seen for the preliminary analyses, most individuals were seeing a dentist for the first time.  No individuals had previous orthodontic treatment.  Most individuals reported brushing at least daily with a toothbrush and toothpaste.

Overall oral hygiene is poor in Jiri.  Participants are scored for the degree of plaque, calculus, and stains apparent on the teeth prior to cleaning, on the general condition of the gingival, on periodontal status as well as the number of carious, missing, or filled teeth.   During the examination, the submandibular and submental lymph glands are palpated for size and tenderness. 

Progress

The Jiri Dental Clinic was established in January 2010 and, closed in the fall of 2011 after seeing close to 1000 participants.  We have begun phenotyping these casts and have presented preliminary data at the American Association of Anatomists meetings in April of 2013. An additional presentation is in preparation for the Society of Craniofacial Genetics and Developmental Biology in October of 2013

For pictures of this beautiful region please go to the pictures page.

Funding

References

Sherwood, R.J., D.L. Duren, J. Subedi, S. Williams-Blangero, The genetics of dentognathic morphology: the Jiri dental project. (Presented at the annual meetings of the Society for Craniofacial Genetics & Developmental Biology, October 22, 2013, Boston, MA).

Sherwood, R.J., D.L. Duren, J. Subedi, S. Williams-Blangero, Dissecting the genetic influence of the orofacial complex. (Presented at the annual meetings of the American Association of Anatomists, April 19-25, 2013, Boston, MA).

Sherwood, R.J., D.L. Duren, J. Blangero, J. Subedi, R. Shrestha, B. Jha, B. Towne, S. Williams-Blangero. 2007. Genetic influence and integration of dental traits.(Presented at the annual meetings of the Paleoanthropology Society, Philadelphia, PA. March 27-28, 2007). Paleoanthropol. 2007:A28.

Sherwood, R.J., D.L. Duren, S. Williams-Blangero, J. Blangero, R. Shrestha, J. Subedi, B. Jha, B. Towne. 2007. Heritability of the human jaw and dentition. Am.J.Phys.Anthropol. Suppl. 44:217.  (Presented at the annual meetings of the American Association of Physical Anthropologists, Philadelphia, PA, March 28-31, 2007).

D.L. Duren, S. Williams-Blangero, J. Subedi,  R. Shrestha, B. Jha, B. Towne, R.J. Sherwood. 2006 Genetic architecture of the human dentognathic complex. (Presented at the annual meetings of the Society of Craniofacial Genetics, New Orleans, LA, October 9, 2006).  Available from: http://www.craniofacialgenetics.org/.

Sherwood, R.J., M.C. Mahaney,  D.L. Duren, L. M. Havill, L.A. Cox, J. Rogers, J. Blangero, T. Dyer, S.A. Cole, S.A. Czerwinski, R.M. Siervogel, B. Towne. 2009. Comparative genomics of the primate craniofacial complex (Presented at the annual meetings of the Society of Craniofacial Genetics, Oct. 20, 2009, Honolulu, HI).  Available from http://www.craniofacialgenetics.org.