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Konnichi-wa! 

Welcome to week seven of my research trip to Japan. Last week I had the honor of presenting my research to Dr. Nakatsukasa’s laboratory group here at Kyoto University. I discussed Hox genes and the various ways that they control limb growth during different phases of development. Then, I shared with them the details of the current project that I am working on with Dr. Nakatsukasa and my mentors at 91�ֿ�.  Dr. Nakatsukasa recently made a brief trip to Nairobi, Kenya over the last two weeks, and he was so kind to bring back souvenirs, including two for me: a beautiful, hand-woven basket and an Australopithecus (Paranthropus) boisei keychain from the Natural History Museum of Kenya! I have been the recipient of such generosity here in Japan, and I will be forever grateful. 

Photo: My presentation for Dr. Nakatsukasa's laboratory. 

Hoxd11and the Pisiform:

As I said last week, this research project is not solely examining long bones of the forelimb, rather it includes multiple areas of inquiry.  Another aspect of the current investigation that I have not yet discussed is Hox expression modules and the carpal bones.  I have previously explained why Hox genes are important for the development of functional growth plates. Hox knock-out experiments have shown that these genes help regulate maturation and proliferation of chondrocytes.  It is thought that the carpals exist in a zone of low Hox expression between the autopod and the zeugopod, and that this is why they are small bones that lack growth plates. However, one exception is the pisiform. In most primates (and mammals in general) the pisiform is longer than other carpals, it has two centers of ossification, and Kjosness et al. (2014) found that the organization of chondrocytes between the centers of ossification suggests the presence of a growth plate.  Some of the same authors show in a later publication that the pisiform falls within the expression territory of Hoxd11, and they hypothesize that the human pisiform has become markedly shortened due to the loss of this growth plate (Reno et al. 2016).  In addition to measuring the long bones of the forelimb, I have measured the weight of the pisiform in various species, and I will be analyzing it’s relationship to the other forelimb elements.  We expect its size to covary with the radius, ulna, and posterior metacarpals.  

Photo: Expression of mouse Hoxd11 from Kjosness et al. (2014). The expression

territory encompasses the four posterior digits, as well as a small region of the carpus

on the ulnar side, at the approximate location of the developing pisiform.

More beautiful sites in Kyoto:

Last weekend I traveled to different parts of Kyoto. I visited Kiyomizu Temple, and then finally tried a matcha (green tea) ice cream cone while shopping nearby! It was oishii (delicious)! I toured Nijo-jo Castle, and then saw the Kinkaku-ji (the “Temple of the Golden Pavilion”), one of the cultural highlights of my trip so far. In the late-afternoon sunlight, it is positively radiant. 

Photos: Kinkaku-ji (left) and Kiyomizu Temple (right).

(Kiyomizu Temple image from )

Tune in next week!

Peace,

Heather