PF664 46/1 HAPLOTYPE IS ASSOCIATED WITH A HIGHER MONOCYTE/LYMPHOCYTE RATIO IN HEALTHY INDIVIDUALS
Authors: Carreño‐Tarragona G. , Silla J.C. , Oliva B. , Chase A.J. , Rouco R. , Ayala R. , García‐Ruiz J.M. , Cross N.C. P. , Martínez‐López J. , Sánchez‐Cabo F. , Fuster V. , Manzanares M. 
Published: June 2019

Background:

The JAK2 46/1 haplotype was described a decade ago. This haplotype has been clearly associated with a higher risk of developing JAK2 positive myeloproliferative neoplasms (MPNs) and according to some studies also to JAK2 negative MPNs. Nevertheless, the mechanism by which the 46/1 haplotype increases MPN risk has yet to be described.

Aims:

The aim of this study was to further characterize the effects of the 46/1 haplotype on clinical, analytical and gene expression of healthy individuals. This could give us new insights into the association with myeloproliferative neoplasms.

Methods:

We haplotyped 509 healthy participants of the PESA (Progression of Early Subclinical Atherosclerosis) Study for the 46/1 haplotype using an endpoint genotyping system. Average age was 48,1 ± 4,08 years old and 86,4% were males. RNAseq data from total blood of these individuals was generated at baseline and 3 years after enrolment in the study. A moderated mixed effects model was used to identify genes which expression changes could be potentially associated with the haplotype of the participants after adjustment by sequencing batch. P‐values were corrected for multiple testing. Gene Enrichment Analysis was performed using the web tool Enrichr (we used Human Gene Atlas for Cell Types and GO Biological Process for Ontologies). Comparisons between traditional risk factors with the haplotype were performed using Chi‐square or Fisheŕs exact test, as appropriate. The association between biochemical measurements with the haplotype were assessed using linear regression model.

Results:

We identified 285 (56%) wild‐type homozygous, 186 (36.5%) heterozygous and 38 (7.5%) 46/1 homozygous. No differences due to sex, age or cardiovascular risk factors were identified.

Complete biochemistry and haemogram data was available for all participants. Correlation of 46/1 haplotype with this data identified a significant association with higher monocyte percentage in visit 1 (p = 0.036) and lower lymphocyte percentage (p = 0.038) in visit 2. Strikingly, we found correlation with a higher monocyte/lymphocyte ratio in both visits (p = 0.031 and p = 0.032 for visit 1 and 2 respectively). No differences were found in biochemical data between genotypes in either visits.

We next analyzed RNAseq data of total blood for both visits. Comparing 46/1 with wild‐type homozygotes we found differences in the expression of 759 (out of 12060) and 871 (out of 12081) genes. For visit 1, 395 genes were upregulated and 364 were downregulated. For visit 2, 350 genes were upregulated and 521 were downregulated. However, these differences were not statistically significant after adjustment for multiple testing.

Nevertheless, we performed a gene enrichment analysis based on functional annotation. In both visits, genes related to the lymphocyte lineage and acquired immunity processes were downregulated while genes related to the myeloid lineage (more specifically monocyte and early erythroid genes) were upregulated (Figure 1).

Summary/Conclusion:

The 46/1haplotype is associated with an unbalance in monocyte/lymphocyte ratio in healthy individuals. The reason for this is unclear, but may relate to inflammatory processes. Finally, there is an enrichment in expression of genes related to the myeloid lineage in whole blood of 46/1 homozygotes. Our data provides novel insights into the physiological consequences of the 46/1 haplotype and offers new clues in our understanding the pathophysiology of MPNs.

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