Many genetic diseases arise each generation because a parent transmits a brand new mutation to a child. Some mutations occur at frequencies 100-1,000 greater than what would be expected based on genome-average rates;many of these mutations are more likely to originate in the father than the mother, and to originate in older fathers than younger fathers (paternal age effect). Apert syndrome is an example of such a disease and is caused by mutations in the receptor tyrosine kinase (RTK) gene FGFR2. The high mutation frequencies could be due to greater than average mutation rates at the causal nucleotide sites, i.e. mutation """"""""hot spots"""""""", or paradoxically, to positive selection on mutated premeiotic testis cells, whereby the mutation provides a growth advantage over the wild-type cells despite the consequences to the offspring. A method is available to distinguish between these two hypotheses by dissecting the testis of an unaffected male and measuring the mutation frequencies in each testis piece. If the mutation site is a hot spot, all testis pieces are expected to have elevated mutation frequencies. If germline selection is responsible, clusters with elevated mutation frequencies, surrounded by testis pieces with much lower mutation frequencies, are expected. For Apert syndrome mutations, in older testis donors, mutation clusters indicating germline selection were found. In younger testis donors, mutation clusters were not found, demonstrating that these clusters, and the mutation frequency, grew in the adult to contribute to the paternal age effect. The demonstration that an increase in disease mutation frequency might be due to germline selection is unprecedented. New disease mutations in different genes that show an unexpectedly high frequency will be studied using the testis dissection approach to distinguish between mutation hot spots or germline selection. First, disease mutations in different RTK genes will be analyzed to establish the relationship between the mutation frequency per germline cell division, the extent of any selective advantage and the magnitude of the observed paternal age effect. The second and third aims will examine disease mutations whose properties might reveal the altered protein functions and signal transduction pathways involved in providing the germline selective advantage. Finally, the fourth aim will develop improved methods for detecting very rare mutation events.

Public Health Relevance

Using a new set of molecular tools we aim to understand the relative roles played by new mutation, paternal age and germline selection in establishing the unexpectedly high population burden of certain relatively well understood genetic diseases. Paternal age has become more recognized as a significant factor in societies where couples are delaying the time when they first have children. Learning about the factors responsible for the unexpectedly high mutation frequencies of the diseases studied in this grant may provide insight into the mechanisms behind the paternal age effect exhibited by less well understood diseases (e.g. autism and schizophrenia). Finally, developing new technologies for rare mutation detection could also be useful in cancer diagnostics and forensics as well as in discovery research.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
3R01GM036745-26S1
Application #
8473558
Study Section
Genetic Variation and Evolution Study Section (GVE)
Program Officer
Krasnewich, Donna M
Project Start
1985-09-01
Project End
2014-08-31
Budget Start
2011-09-01
Budget End
2012-08-31
Support Year
26
Fiscal Year
2012
Total Cost
$9,294
Indirect Cost
$3,627
Name
University of Southern California
Department
Biology
Type
Schools of Arts and Sciences
DUNS #
072933393
City
Los Angeles
State
CA
Country
United States
Zip Code
90089
Eboreime, Jordan; Choi, Soo-Kung; Yoon, Song-Ro et al. (2016) Estimating Exceptionally Rare Germline and Somatic Mutation Frequencies via Next Generation Sequencing. PLoS One 11:e0158340
Arnheim, Norman; Calabrese, Peter (2016) Germline Stem Cell Competition, Mutation Hot Spots, Genetic Disorders, and Older Fathers. Annu Rev Genomics Hum Genet 17:219-43
Fischer, Jared M; Calabrese, Peter P; Miller, Ashleigh J et al. (2016) Single cell lineage tracing reveals a role for Tgf?R2 in intestinal stem cell dynamics and differentiation. Proc Natl Acad Sci U S A 113:12192-12197
Yoon, Song-Ro; Choi, Soo-Kung; Eboreime, Jordan et al. (2013) Age-dependent germline mosaicism of the most common noonan syndrome mutation shows the signature of germline selection. Am J Hum Genet 92:917-26
Shinde, Deepali N; Elmer, Dominik P; Calabrese, Peter et al. (2013) New evidence for positive selection helps explain the paternal age effect observed in achondroplasia. Hum Mol Genet 22:4117-26
Choi, Soo-Kyung; Yoon, Song-Ro; Calabrese, Peter et al. (2012) Positive selection for new disease mutations in the human germline: evidence from the heritable cancer syndrome multiple endocrine neoplasia type 2B. PLoS Genet 8:e1002420
Qin, Jian; Subramanian, Jaichandar; Arnheim, Norman (2009) Detection of meiotic DNA breaks in mouse testicular germ cells. Methods Mol Biol 557:165-81
Yoon, Song-Ro; Qin, Jian; Glaser, Rivka L et al. (2009) The ups and downs of mutation frequencies during aging can account for the Apert syndrome paternal age effect. PLoS Genet 5:e1000558
Arnheim, Norman; Calabrese, Peter (2009) Understanding what determines the frequency and pattern of human germline mutations. Nat Rev Genet 10:478-88
Tiemann-Boege, Irene; Curtis, Christina; Shinde, Deepali N et al. (2009) Product length, dye choice, and detection chemistry in the bead-emulsion amplification of millions of single DNA molecules in parallel. Anal Chem 81:5770-6

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