bioRxiv preprint doi: https://doi.org/10.1101/2021.04.12.439429; this version posted April 12, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license.

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3 The growth hormone gene has evolved independently in African Pygmy minutoides

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5 Sumito Matsuya1, Hiroyuki Imai2, Yasuo Kiso2, Ken Takeshi Kusakabe2 Kiyoshi Kano1*

6 1 Laboratory of Developmental Biology, Joint-Faculty of Veterinary Medicine, Yamaguchi University,

7 Yamaguchi 753-8515, Japan

8 2 Laboratory of Veterinar Anatomy, Joint-Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi

9 753-8515, Japan

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11 Corresponding author.: E-mail: [email protected]

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13 Running head: GROWTH HORMONE IN MUS MINUTOIDES

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1 bioRxiv preprint doi: https://doi.org/10.1101/2021.04.12.439429; this version posted April 12, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license.

15 Abstract

16 Mus minutoides (the ) is one of the smallest . We determined the nucleotide

17 sequence of the growth hormone (Gh) gene and the sequence of the putative coding region in M.

18 minutoides, where is predicted to be distinct in the functional and transcriptional regulatory regions

19 between M. minutoides and Mus musculus (the ). To investigate the evolutionary characteristics

20 of Gh in M. minutoides, we constructed a phylogenetic tree based on the putative amino acid sequences of

21 Gh in M. musculus and mammals by neighbor-joining method, suggesting that Gh diverged relatively

22 earlier than other Mus genus and may have evolved independently in M. minutoides. Furthermore, analysis

23 of Gh gene expression levels showed a tendency to be higher in M. minutoides than in M. musculus. Our

24 results suggest that Gh may have evolved independently in M. minutoides and may have different functions

25 and signaling in Mus genus.

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27 Keywords: body size, evolution, growth hormone, mouse, Mus minutoides

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2 bioRxiv preprint doi: https://doi.org/10.1101/2021.04.12.439429; this version posted April 12, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license.

30 Mammals have various body sizes, ranging from large whales to small . Each also has an

31 inherent size, but it is not clear how this is determined and maintained. Mus minutoides (African pygmy

32 mouse) is one of the smallest mammals in the world, measuring about 30 mm in body length and about 3

33 grams in body weight. M. minutoides originally inhabit the south of Saharan in Africa and is now bred as a

34 pet in many countries [6, 11] . The sexual maturity of M. minutoides is about 8 weeks old, the

35 gestation period is about 20 days, and the lifespan is about 2 years [17], which is similar to that of the

36 common laboratory mice, but the of M. minutoides have unique characteristics that differ from

37 those of Mus musuclus. M. minutoides can b