Down syndrome is caused by an abnormality in the way that cells divide. This results in a child having an extra copy of one of their chromosomes, called chromosome 21.
This extra chromosome can be in any of the 23 pairs of chromosomes, but it is most common in trisomy 21, which accounts for 95% of all cases.
What is Trisomy 22?
A 24-year-old chimp named Kanako has been diagnosed with a genetic condition that mimics Down Syndrome in humans. She has a third copy of chromosome 22. This chromosomal defect has stunted her growth, left her blind and resulted in a congenital heart disease.
She’s also the longest-living chimp with this disorder, scientists report in Primates. Her chromosomal abnormality was discovered following a trail of evidence that began with a physical exam in 2014, which showed she had a defect in the wall of her heart that separated the top two chambers.
Her doctors were able to analyze her chromosomes and eventually confirm she has trisomy 22. It’s the second confirmed case of this chromosomal defect in a chimpanzee, according to researchers.
The first chimp with trisomy 22 was found in 1969, but the monkey didn’t live long enough to see its second birthday. Now, a Japanese research team has identified another chimp with this condition.
Like human trisomy 21, apes can have a third copy of chromosome 22, which causes the ape’s cells to contain 46 chromosomes instead of the usual 23 pairs. The extra chromosome can affect the development of the body, brain and organs.
As a result, apes can have a range of unusual features. One of the most common is craniofacial dysmorphology, which involves an overall smaller skull size. The condition can also affect the ears and the limbs.
Other features include an open mouth, flat nasal bridge and epicanthal folds (the folds between the nostrils). This can cause a person to have difficulty breathing.
The condition can also lead to a wide array of cognitive impairments, including problems learning and memory. In fact, it’s one of the most common genetic causes of mental retardation in people.
Kanako’s chromosomal disorder came to light after her caretakers noticed some issues, such as a gap in the wall of her heart that separates the top two chambers. She has been undergoing regular tests to monitor her health, and the latest results have confirmed she has trisomy 22.
Trisomy 22 in Chimpanzees
Trisomy 22 has been reported in several species of monkeys, including chimpanzees and gorillas. It is also known as down syndrome and is caused by the chromosomal abnormality band q22.3 on chromosome 21 in humans.
Although many monkeys are affected by down syndrome, only a few have been studied in detail. The first such case was reported in 1969. Now, researchers have discovered a second case of trisomy 22 in a chimpanzee living at a sanctuary in Japan.
Kanako, a female chimpanzee at the Kumamoto Sanctuary Wildlife Research Center in Japan, has an extra chromosome on her DNA. This chromosome was confirmed by Q-banding and multicolor fluorescence in situ hybridization (FISH) techniques.
She is blind, and her chromosomes have been examined to determine the cause of her condition. The results have revealed an atrial septal defect-a hole in the wall that separates the top two chambers of her heart-and she also has congential heart disease.
The atrial septal defect is similar to a ventricular septal defect in humans, which can lead to a sudden death. Moreover, a cataract is present on her retina, which is also common in people with down syndrome.
Her facial features are also similar to those of a person with Down syndrome, and she has the characteristic ears, eyes, and nose. She also has abnormal behavior, including unwariness towards humans and poor concentration.
She has been given the opportunity to interact with another chimp once a month, and has become calm and friendly toward her. She is still very young, and has not yet lost her mobility.
Since a significant portion of her genetic makeup was unknown, Dr Hirata says that she will be monitored carefully for the rest of her life. ‘We will examine her heart and brain at regular intervals. Her social behavior will be analyzed, and she will be compared with other chimpanzees. Hopefully, the findings will help us understand what happens to her as she grows older,’ she said.
The genome sequencing of chimpanzees has provided a rich set of data and opportunities for examining different kinds of molecular processes that affect human and chimpanzee differences. Among these processes are nucleotide substitutions, gene duplications, insertions and deletions, chromosomal rearrangements, and potential karyotypic changes. These insights will help scientists in a number of areas, from determining the biological basis of human traits to identifying potential drug targets.
Trisomy 22 in Gorillas
While trisomy 22 is a rare condition, there are two known cases of monkeys with the disorder. One of the cases involved a baby chimp in Tanzania with a variety of symptoms that were similar to those found in people with Down syndrome, but chromosomal tests could not be done.
Another case was a baby gorilla in Bwindi National Park, Rwanda, who had severe behavioral problems. She was not able to stand up on her own and struggled with walking. She also had a lack of coordination and weak legs.
Several factors contributed to her diagnosis, including the lack of genetic screening for Down syndrome, and a lack of understanding about the disease in the wild. In addition, the chimp was inbred with other chimps, which may have caused her to develop the condition.
However, her lack of abnormalities in daily caretaking before she was one suggests that there was no significant retardation. This is important because it helps scientists learn more about how often the condition can occur in chimpanzees and what it does to their development.
In order to understand the evolutionary origins of Down syndrome, researchers used a probe that is used on human chromosome 21 band q22.3 (Figure 2B and Supplementary Figure 7A). This particular probe was found to be conserved between chimpanzee, bonobo, gorilla, and orangutan, which is very interesting.
While a lot of research has been done on chromosome 21 band q22.3 in humans, this is the first time that a chromosome-specific probe has been used to study the same region in other primates. In addition to chimpanzee, bonobo, and gorilla, orangutans have also been studied.
This study examined Y-chromosome microsatellite locus variation in eastern and western lowland gorillas, as well as the small Cross River gorilla population and several localities within the Grauer’s gorilla range. Y-chromosomal haplotypes were not characterized by distinct clusters, suggesting structure in the ancestral populations with subsequent mixing due to male dispersal for western lowland gorillas and postisolation migration or incomplete lineage sorting for eastern gorillas.
We also analyzed Y-chromosomal mtDNA data from the same individuals, and we found that the average genetic distances of the mtDNA regions were similar for mountain gorillas and Grauer’s gorillas, but not for Cross River gorillas. This was in contrast to other mtDNA studies of gorillas, which showed more diversity in the mtDNA regions of eastern gorillas than those of mountain gorillas. This is likely because mtDNA is more stable than autosomal DNA and has been around longer.
Trisomy 22 in Orangutans
Trisomy 22 is a condition that can develop in chimpanzees, gorillas and orangutans. This chromosomal abnormality is similar to Down syndrome in humans, and can cause significant delays in the development of normal cognitive abilities and social skills.
Japanese researchers have confirmed the second case of a chimpanzee with trisomy 22. This chimp, named Kanako, was born in captivity and is now 24 years old. She is the longest living chimp with this chromosomal defect that scientists know of, and her condition was recently documented in the journal Primates1.
The genetic disorder is caused by a chromosomal mutation on chromosome 22. Scientists are not sure how common this condition is among chimpanzees, but it has been reported in Tanzania and other parts of Africa.
Since the first known chimpanzee with trisomy 22, scientists have not been able to find any other examples of this rare condition in the wild. However, there are several captive chimpanzees with this condition.
In one of the cases, a chimp named Knuckles, was found to have a chromosomal abnormality that caused her to be very clumsy in her locomotion and had difficulty in social interaction with other chimpanzees. Azalea, a young rhesus monkey, was also found to have a chromosomal defect that caused her to be socially inept.
Despite the difficulties, researchers have found some positive results in the study of orangutans with trisomy 22. For example, they have shown that this gene is associated with a number of important genes for learning and memory.
They have also shown that this chromosomal abnormality can be caused by a mutation in the CFTR gene. This gene controls the function of the cilia in the respiratory system.
CFTR is also involved in the immune system, which may be why the orangutan has a respiratory disorder. This CFTR variant is also present in some human cystic fibrosis patients and has been linked to the severe form of the disease. The authors hope that genetic screening of the captive orangutan population could prevent transmission of this lethal variant and aid in the conservation of this endangered species.