Cloning, sequencing and functional expression of zebra (Equus burchelli) LH.

This research paper investigates the structures and functions of the gonadotrophin family in zebras, specifically luteinizing hormone (LH), and compares its follicle-stimulating hormone (FSH) activity with that of donkeys and horses. Despite similarities at the amino acid level, the zebra’s LH has no detectable FSH activity, indicating potential key differences in certain amino acids.

Cloning and Sequencing of Zebra LH

• The study begins with the cloning and sequencing of the luteinizing hormone from the common zebra (Equus burchelli) for further investigation.
• This is done by employing reverse transcription-PCR from the pituitary gland RNA of the zebra.
• The primary aim here is to delve deeper into understanding the structure and functioning relationships of this gonadotrophin family, particularly as they relate to very high amino acid sequence identity with horse LH and donkey LH.

Functional Expression of Zebra LH

• After the sequencing, the LH from the zebra was expressed in COS-7 cells, a commonly used cell line in labs for the purpose of expressing eukaryotic genes.
• Directly after its expression, its LH and FSH activities were assessed in a rat Leydig cell bioassay (for LH) and in a cell line stably expressing the human FSH receptor bioassay (for FSH).
• Upon comparison, the recombinant zebra LH was found to display similar LH activity to that of the previously studied recombinant donkey and horse LHs.

Amino Acids and FSH Activities

• Detailing on the functionalities, the study discovered that the zebra LH had no detectable FSH activity. This is strikingly different from the donkey and horse LH sequences which have prominent FSH activity.
• The LH amino acid sequences of the donkey, horse, and zebra show very little variability, which points towards few defining amino acids that could potentially explain the marked difference in their FSH activities.

Phylogenetic Analysis

• The research concludes by measuring the phylogenetic distance (the measure of genetic separation between species) between the zebra, the donkey, and the horse.
• Based on the difference in the FSH bioactivity and the percentage identity between the sequences, the study suggests that the common zebra is phylogenetically closer to the donkey than it is to the horse.