Chimpanzee Kanako
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EDITORIAL
Chimpanzee Kanako Satoshi Hirata1 Published online: 25 August 2020 © Japan Monkey Centre and Springer Japan KK, part of Springer Nature 2020
Chimpanzee Down Syndrome Kanako was a female chimpanzee who was born on 2 June 1992 at a facility in Kumamoto, Japan, which was then owned by a pharmaceutical company. She passed away peacefully in the morning of 12 February 2020 at 27 years of age. As reported in this journal (Hirata et al. 2017), Kanako was a blind chimpanzee with a chromosomal abnormality: chimpanzee trisomy 22. The total number of chromosomes in a normal chimpanzee is 48 (24 pairs), compared to 46 (23 pairs) in humans (Jauch et al. 1992). To put it simply, chimpanzee chromosomes 12 and 13 are merged in human chromosome 2. The remaining chromosomes in chimpanzees and humans have a one-to-one correspondence. Chimpanzee chromosome 22 corresponds to human chromosome 21 (Richard and Dutrillaux 1998). Kanako had an extra copy of chromosome 22, i.e., she had three copies, whereas normal chimpanzees have only two. In humans, having an extra copy of chromosome 21 causes Down syndrome, or trisomy 21. Kanako had chimpanzee trisomy 22, which is equivalent to human trisomy 21. After Kanako was born she at first appeared to be developing like a normal baby chimpanzee, although a caregiver noted that she was somewhat inactive and seemingly had less power in her hands and feet than normal; she was also unusually quiet. Her weight at birth was 1940 g, which is above average for newborn chimpanzees. Kanako’s mother stopped taking care of her when she was about 5 months old, so she was reared by humans from then on. Shortly before 1 year of age, Kanako began to develop cataracts, leading to increasing loss of eyesight. At around 1 year of age she began to search for food with her mouth, a sign of
loss of vision. One year later she underwent cataract surgery. However, Kanako repeatedly rubbed her eyes after surgery, resulting in postoperative inflammation. The inflammation caused pupillary block, which led to glaucoma. Kanako’s eyesight got progressively worse, and when she was 7 years old she began exploring her surroundings exclusively by touch, at which point she was declared blind. No-one knew that Kanako had a chromosomal abnormality until she was 22 years old. Although a genetic disorder had been suspected, no formal test had been conducted because genetic diseases are not curable. Thus there appeared no real advantage to finding out the genetic cause of Kanako’s condition. Kanako was taken care of by the same personnel who looked after the other chimpanzees at the facility. In 2011, ownership of the facility was transferred from the pharmaceutical company to Kyoto University; I will return to this later. A new diagnostic ultrasound imaging device was acquired, which allowed the chimpanzees to be given advanced physical check-ups. Kanako’s echocardiogram showed abnormal blood flow, which indicated a hole in the wall of her heart.
S. Hirata: Vice Editor-in-Chief, PRIMATES. * Satoshi Hirata hirata.satoshi.8z@k
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