Download File - Prader

Holly Heacock
Specific Aims
Prader-Willi Syndrome (PWS) is a genetic disorder that affects 1 in 15,000 individuals worldwide and is the
most common genetic cause of obesity in children. PWS individuals progress through two main stages of
symptoms: The first is characterized by decreased muscle tone and the second by insatiable hunger and
increased weight, among other symptoms(1). PWS is caused by a deletion on the paternal chromosome 15
resulting in the loss of five genes' expression(2). One of these genes is necdin, a DNA binding protein that
functions mostly in neural cell differentiation but has also been traced to the differentiation of other cells,
including fat and muscle cells(3). Necdin normally promotes muscle cell differentiation and inhibits fat cell
differentiation (4). However, it is unknown if the loss of necdin causes a transition from muscle cell formation to
increased fat cell formation at a certain point in development, as seen in Prader-Willi Syndrome.
My primary goal is to determine the role of necdin in the transition from muscle to fat cell differentiation in
development.
My hypothesis is that the loss of necdin regulates the transition from muscle cell differentiation to fat cell
differentiation during development in Prader-Willi Syndrome individuals.
My long term goal is to gain a better understanding of necdin's role in the obesity seen in PWS in order to
diagnose the disorder earlier and to design preventative treatments.
Aim 1: Identify expression of fat and muscle regulatory genes in wild-type (WT) and necdin mutant mice.
Approach: We will use RNAseq to analyze expression of the previously mentioned genes in tissues of both
WT and mutant mice. Hypothesis: Fat regulatory genes will be at higher expression levels than muscle
regulatory genes in the mutant and vice versa in the WT. Rationale: This information tells us relative amounts
of muscle and fat cell regulatory gene expression with and without necdin so that we may infer amounts of fat
cell vs. muscle cell differentiation.
Aim 2: Determine if the loss of necdin contributes to muscle cell loss and fat cell accumulation at a certain
stage in development.
Approach: Using mass spectrometry, we will analyze relative abundance of muscle and fat regulatory proteins
taken from muscle and fat tissues at different stages of development in both the WT and necdin mutant mice.
Hypothesis: The amount of fat regulatory proteins will increase significantly at a specific point in development
in necdin mutant mice. Rationale: This information is important to understanding the timescale for muscle and
fat cell development for clinical diagnosis.
Aim 3: Identify necdin interaction partners with fat and muscle cell regulatory proteins throughout
development.
Approach: We will use STRING to analyze already known interaction partners, and use a yeast two-hybrid
method to find novel interaction partners, taking proteins from different points of development. Hypothesis:
Necdin will interact with many muscle cell regulatory proteins and fewer fat cell regulatory proteins, but new fat
cell regulatory proteins will be found. Rationale: This information tells us what other proteins necdin normally
works with in muscle and fat cell differentiation and how these interactions may change throughout
development.
Prader-Willi Syndrome is becoming a more well-known genetic disorder, especially as it contributes to
childhood obesity. By learning more about how necdin may play a role in the formation of fat cells, contributing
to the obesity phenotype of PWS, we may gain a better understanding of how to create further treatments so
as to prevent death due to obesity.
Holly Heacock
Specific Aims
References
1) Basic Facts About PWS. (n.d.). Retrieved April 6, 2015, from http://www.pwsausa.org/about- pws/basicfacts-about-pws
2) Jay, P., Rougeulle, C., Massacrier, A., Moncla, A., Mattel, M., Malzac, P., ... Muscatelli, F. (1997). The
human necdin gene, NDN, is maternally imprinted and located in the Prader-Willi syndrome
chromosomal region. Nature Genetics, 17, 357-361.
3) Macdonald, H., & Wevrick, R. (1997). The Necdin Gene is Deleted in Prader-Willi Syndrome and is
Imprinted in Human and Mouse. Human Molecular Genetics,6(11), 1873-1878.
4) Bush, J., & Wevrick, R. (2012). Loss of the Prader–Willi obesity syndrome protein necdin promotes
adipogenesis. Gene, 45-51.