Aims

1. The role of ESR1 rs77757956 in skeletal development

A. We will determine whether the interaction between ESR1rs77757956, TBLH ABMC and puberty in peri-pubertal girls described above results in a lower TBLH ABMC in post-pubertal girls with the TA/AA genotype, but not boys, by analyzing these relationships in approximately 5000 15 year-old children from ALSPAC.Whethercortical bone geometry in post-pubertal girls is also affected will be addressed, by analyzing relationships withpQCT parameters.

B. Whether equivalent relationships between ESR1rs77757956 and skeletal development are observed in other populations will be investigated, by repeating these analyses in a cohort of girls from Finland with repeated DXA and pQCT measures during puberty.

C.We plan to study whetherrs77757956affects peak bone mass in adulthood, by analysing associations with DXA measures in around 3000 mothers from ALSPAC, and 4000 women from the St Thomas' Twin cohort. Further analyses will be performed in these cohorts to examine possible effects of this polymorphism on fracture and obesity risk in adulthood.

D.As a prelude to future functional studies, we will determine whetherrs77757956 influences skeletal phenotypes directly, or as a consequence of linkage with other SNPs,following genotyping of ALSPAC children for the 6 other SNPs with which this is in LD.

2. The role of other ESR1 polymorphisms in skeletal development

We will determine if other ESR1 gene variants influence skeletal development or peak bone mass, by exploring associations between DXA measures and common haplotype-tagging ESR1 SNPs analysed as part of a genome-wide association study (GWAS) in a 10% sub-group of ALSPAC children, and in 4000 women from the St Thomas' Twin cohort. Whether associations can be replicated in other children (remainder of ALSPAC, cohorts of peripubertal girls in Finland and postpubertal boys in Sweden) or adults (ALSPAC mothers) will subsequently be investigated.

3. The influence of ESR1 polymorphisms on ERa expression

We will evaluate the feasibility of using ALSPAC cell lines to examine whether ESR1 genotypes influence ERa expression, by investigating whether maternal/child EBV-transformed B lymphocyte cell lines express ERa mRNA at levels which can be reliably quantitated using the ARCS high throughput method. Further studies will be performed in light of these findings, relating ESR1 genotype to ERa expression levels in cell lines from ALSPAC children