Seasonal adaptations of the hypothalamo-neurohypophyseal system of the dromedary camel

Abstract

The “ship” of the Arabian and North African deserts, the one-humped dromedary camel ( Camelus dromedarius) has a remarkable capacity to survive in conditions of extreme heat without needing to drink water. One of the ways that this is achieved is through the actions of the antidiuretic hormone arginine vasopressin (AVP), which is made in a specialised part of the brain called the hypothalamo-neurohypophyseal system (HNS), but exerts its effects at the level of the kidney to provoke water conservation. Interestingly, our electron microscopy studies have shown that the ultrastructure of the dromedary HNS changes according to season, suggesting that in the arid conditions of summer the HNS is in an activated state, in preparation for the likely prospect of water deprivation. Based on our dromedary genome sequence, we have carried out an RNAseq analysis of the dromedary HNS in summer and winter. Amongst the 171 transcripts found to be significantly differentially regulated (>2 fold change, p value <0.05) there is a significant over-representation of neuropeptide encoding genes, including that encoding AVP, the expression of which appeared to increase in summer. Identification of neuropeptides in the HNS and analysis of neuropeptide profiles in extracts from individual camels using mass spectrometry indicates that overall AVP peptide levels decreased in the HNS during summer compared to winter, perhaps due to increased release during periods of dehydration in the dry season.

Old World camels in a modern world – a balancing act between conservation and genetic improvement

“…The first genome was published for C. ferus in 2012 (GCA_000311805.2, Jirimutu et al 2012) followed by two domestic Bactrian camel genomes (GCA_000604445.1, Palmieri 2014 andGCA_000767855.1, Wu et al 2014). Two of the three available dromedary genomes (GCA_000767585.1, Wu et al 2014 andGCA_000803125.1, Fitak et al 2016a,b) show a high assembly quality (few scaffolds, long N50), whereas the third genome is more fragmented (GCA_001640815.1, Alim et al 2019). Improved dromedary genome assemblies on a chromosome level using a combination of Illumina short reads, PacBio reads, Dovetail Hi-C/Chicago and 10X Genomics Chromium sequencing, respectively, have been presented (Brooks et al 2019) and are available now .…”

Improving Illumina assemblies with Hi‐C and long reads: An example with the North African dromedary

“…To assess the quality of the new assembly, we aligned 10 sets of paired‐end RNA‐Seq reads (Alim et al, ) to the original assembly (CamDro1), to the new assembly (CamDro2), and to several controls: C. dromedarius (RefSeq version ‐ ), C. bactrianus (), C. ferus () and Bos taurus (cattle) (). The 10 RNA‐Seq data sets comprise a 2 × 2 factorial experiment: summer versus winter seasons and supraoptic nucleus (SON) versus neurointermediate lobe (NIL) brain tissues, with n = 3 replicates in each class.…”

“…For ESTs, we assembled transcripts from two dromedary RNA‐Seq experiments (Sequence Read Archive accession: SRP017619; Alim et al, ). We performed adapter and quality trimming on raw demultiplexed paired‐end reads using bbduk v. 37.25 (https://sourceforge.net/projects/bbmap/), using the following settings: ktrim = r, k = 23, mink = 11, hdist = 1, tpe, tbo, qtrim = rl, trimq = 15.…”

“…Read alignments (Dovetail Chicago and Dovetail Hi‐C reads mapped to original North African dromedary genome assembly, CamDro1) are available upon request. Dromedary RNA‐Seq sequences are from Alim et al, ; NCBI BioProject . CamDro2 gene annotations, predicted mRNA and proteins, assembly for gene annotations, CamDro1 assembly improved by Dovetail Genomics Chicago and Hi‐C libraries, and RH V. pacos probe sequences are available from Dryad (https://doi.org/10.5061/dryad.6rp36b6).…”

“…To assess the quality of the new assembly, we aligned 10 sets of paired-end RNA-Seq reads (Alim et al, 2019) to the original assembly (CamDro1), to the new assembly (CamDro2), and to several controls:…”