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Scientists Are Cracking Ancient Chromosomal Complications
In biological terms, being male typically means you have XY chromosomes, and being female typically means you have XX chromosomes. But it doesn't always work out that way. Sometimes, a person can be born with too many or too few chromosomes, which is known as "aneuploidy" and can cause Turner (missing X), Klinefelter syndrome (XXY), and Jacob's syndromes (XYY). And while we know these abnormalities are not a modern development, finding prehistoric evidence of these diseases has proven difficult, as DNA erodes over time and becomes contaminated by other ancient samples or by the people handling it.
To get around these problems, scientists from the University of Oxford, University of York, and Oxford Archaeology have developed a new method to count chromosomes in ancient genomes. This recently allowed them to identify the first prehistoric case of Turner's syndrome, as well as the oldest-known person to have Jacob's syndrome (from the early Medieval period). The result of their work was published Thursday in the journal Communications Biology.
Related Story"It's hard to see a full picture of how these individuals lived and interacted with their society, as they weren't found with possessions or in unusual graves," PhD student and study co-author Kakia Anastasiadou said in a press release, "but it can allow some insight into how perceptions of gender identity have evolved over time."
To count these chromosomes, experts analyzed a large data set—part of the Thousand Ancient British Genomes project—and used a new computational method to identify certain aneuploidies, along with instances of contamination. As a result, the team found individuals from as far back as the Iron Age (roughly 2,5000 years ago) to the post-Medieval period just 250 years ago.
Related StoryAdditionally, these extraneous or missing sex chromosomes can interfere with a human's natural sexual progression. For example, the bones of the person with Turner's syndrome indicated puberty and menstruation had not yet begun, even though the age of the remains was between 18 to 22 years old.
"Ancient DNA can contribute to our understanding of chromosomal sex in the past, its relationship with gender, and allow for the identification of non-binary chromosomal sex via investigation of the number of sex chromosomes detected in an individual's karyotype (set of chromosomes)," the paper reads. "Deploying genomic data for sex identification can surpass limitations in the sex estimation methods that rely on osteological features."
The researchers hope that an "ever-increasing number of ancient genomes" will help us understand the genomic diversity of the past and present and offer a new, genetic lens through which to view our history.
Darren lives in Portland, has a cat, and writes/edits about sci-fi and how our world works. You can find his previous stuff at Gizmodo and Paste if you look hard enough.
What You Should Know About Mosaic Turner Syndrome
Turner syndrome is a chromosomal condition involving a person's sex chromosomes. It is considered mosaic when an X chromosome is missing in some cells in people who have two X chromosomes.
Turner syndrome is a chromosomal condition involving a person's sex chromosomes. Turner syndrome results when one of the X chromosomes (sex chromosomes) is missing or partially missing following conception.
In mosaic Turner syndrome, an X chromosome is missing in some cells in people assigned female at birth.
Keep reading to learn more about what causes mosaic Turner syndrome, what the symptoms might be, and what treatments are available.
Chromosomes are what carry genetic information (also called DNA) from each cell throughout the human body. Each person is born with 23 pairs of chromosomes — 46 total — including one pair of sex chromosomes, X and Y.
Turner syndrome affects people who were assigned female at birth. While people assigned female at birth typically have two X chromosomes (XX), people with Turner syndrome have just one X chromosome.
Because so much genetic information is missing at such an early stage of development, Turner syndrome can cause a variety of medical and developmental concerns, including failure of the ovaries to develop, heart defects, and short height.
There are two main types of Turner syndrome:
In general, symptoms for people with mosaic Turner syndrome tend to be less severe than symptoms for people with complete Turner syndrome. This is because the number of cells that are affected by the missing or deficient X chromosome is fewer with mosaicism.
Some cells contain the usual two XX chromosomes and, therefore, do not contribute to health issues.
Symptoms may vary greatly between people with mosaic Turner syndrome. Some people may not even realize they have this condition until puberty or later in life.
Symptoms may include:
In addition to these symptoms, a person with mosaic Turner syndrome may have certain physical characteristics, including:
Again, these symptoms may be milder than people experience with complete Turner syndrome. A 2018 study revealed that people with the mosaic (partial) form tended to be closer to average height with fewer reproductive and heart issues.
Turner syndrome is rare. It affects roughly 1 in every 2,000 to 2,500 female births across the globe.
The mosaic form of this condition is caused by a partial loss of the second X chromosome. The one-chromosome form is caused by a complete loss of the second X chromosome.
A 2013 study found that between 30% and 40% of people with Turner syndrome have the mosaic form.
What causes the loss of this second sex chromosome isn't fully understood yet. Researchers believe it may happen at random during reproduction. It could occur soon after the sperm meets the egg or early in fetal development.
Turner syndrome does not appear to be genetically inherited. This means it does not run in families.
Diagnosis is often made after a baby is born, in either childhood or adolescence. The physical features of infants with Turner syndrome may be recognizable at birth or emerge during infancy.
If your child shows signs after birth, their pediatrician may order tests, such as:
In some cases, a doctor may diagnose Turner syndrome before a baby is born through prenatal genetic testing. In particular, karyotyping may be performed by sampling a mother's blood, bone marrow, or other tissue that can identify any chromosomal abnormalities in the fetus.
Ultrasound may also help doctors diagnose Turner syndrome during pregnancy. Some babies may have lymphedema (swelling) or issues with the kidneys or the heart that are visible on prenatal ultrasounds.
There's no cure for Turner syndrome. Instead, treatment aims to address whatever signs or symptoms a person with Turner syndrome is experiencing. Treatment varies by the person and their needs.
A 2018 study involving people with mosaic Turner syndrome found that treatment may not be necessary — particularly in cases when the syndrome is found by chance.
This means some people may have mosaic Turner syndrome that doesn't cause symptoms or health issues, so there's no need for any treatment.
Otherwise, treatment options may include:
Symptoms of mosaic Turner syndrome tend to be milder than those of complete Turner syndrome. As a result, people with this condition may lead relatively healthy lives.
Early diagnosis and treatment can help with growth and development issues before and during puberty. That said, not all people with mosaic Turner syndrome will have delays in their development. Or if they do, these issues may only be minor.
Do people with mosaic turner syndrome have difficulties with fertility?Most people with mosaic Turner have either reduced fertility or infertility. In vitro fertilization may help address fertility issues.
However, people with mosaic Turner syndrome who do become pregnant are at risk of blood pressure–related complications, which can lead to premature birth or fetal growth restriction.
Pregnancy in people with mosaic Turner syndrome is also associated with an increased risk of maternal complications, including heart conditions like aortic dissection and aortic rupture.
Is there a relationship between mosaic Turner syndrome and autism?Researchers are exploring the potential link between Turner syndrome and autism. In one British study from 2018, the rate of autism in people with Turner syndrome was 21% compared with the U.K. Rate in females of 0.3%.
Mosaic Turner syndrome is a developmental abnormality involving the sex chromosomes. Turner syndrome results when one of the X chromosomes (sex chromosomes) is missing or partially missing following conception.
Treatment can help with a person's specific health issues but may not be necessary if symptoms are mild.
People with this condition may have a range of health and development issues, but they generally may lead healthy lives.
Scientists Identify First Known Prehistoric Person With Turner Syndrome
Enlarge / The cranium of an individual with mosaic Turner syndrome from an Iron Age site in Somerset, UK. K. Anastasiadou et al. 2024 reader comments 73Turner syndrome is a genetic condition in which a (female) person has only one X chromosome instead of two. Scientists have used a new computational method for precisely measuring sex chromosomes to identify the first prehistoric person with this syndrome dating back some 2,500 years ago, according to a recent paper published in the journal Communications Biology. The team identified four other individuals with sex chromosomes outside the usual XX or XY designations: an early medieval individual with Jacobs syndrome (XYY) and three people from various periods with Klinefelter syndrome (XXY). They also identified an Iron Age infant with Down syndrome.
"It's hard to see a full picture of how these individuals lived and interacted with their society, as they weren't found with possessions or in unusual graves, but it can allow some insight into how perceptions of gender identity have evolved over time," said co-author Kakia Anastasiadou, a graduate student at the Francis Crick Institute.
Added co-author Rick Schulting, an archaeologist at the University of Oxford, "The results of this study open up exciting new possibilities for the study of sex in the past, moving beyond binary categories in a way that would be impossible without the advances being made in ancient DNA analysis."
According to the authors, the emergence of ancient genomics "has revolutionized our ability to examine human biology over thousands of years, providing insight into phenotypic variation, social stratification, and their impact on health throughout history." When it comes to determining sex identification of ancient remains, genomic data can often overcome some of the limitations of traditional osteological analysis, which is less useful if a skeleton is incomplete or for analyzing non-adult remains. There are several publicly available tools for doing ancient DNA analysis, but they are less useful for detecting extra or missing sex chromosomes.
AdvertisementAnastasiadou et al. Relied on a large database of ancient DNA collected as part of the Thousand Ancient British Genomes project. Their new computational technique involved determining a predicted baseline number of X and Y chromosomes one would expect to see and comparing that to a careful counting of the exact number of X and Y chromosomes present in the samples. They combined this technique with osteological methods.
The skeleton of a young adult female—age was determined based on the wear of the teeth—found at the Charterhouse Warren site in Somerset—was dated back to the Early Iron Age. The genetic analysis showed that some cells had one X chromosome and others had the usual two, known as mosaic Turner syndrome. Women with Turner syndrome generally undergo human growth hormone and estrogen replacement therapy to boost height and trigger the onset of puberty, respectively. The remains included a partial skull, which showed marked pitting in the orbits—evidence of chronic intestinal hemorrhage, often the result of anemia, although there is a possible link with Turner syndrome. Osteological analysis revealed evidence of delayed growth, and the woman was unlikely to have gone through puberty and started menstruating.
The male infant had an extra chromosome 21 (a sign of Down syndrome) and was found at the Wetwang Slack site, buried in the ditch of a square barrow along with an adult female, although the two were not necessarily related since infants were often buried in existing burrows, per the authors. The skeleton with an extra Y chromosome also showed osteological evidence consistent with Jacobs syndrome (male, 46+ years, dated 680 to 890 CE); it was found at the Lincoln Eastern Bypass site in Lincolnshire.
AdvertisementThe three skeletons that showed evidence of Klinefelter syndrome were all buried during different periods according to the burial customs of their day. One skeleton (male, 17–19 years, circa 450 BCE) was found at an Iron Age cemetery site called Wetwang Slack in Yorkshire; another (male, 36–45, 12th–13th century) came from a medieval cemetery under Longwall Quad at Magdalen College, Oxford; and yet another (16–19 years, 18th–19th century) was found at Trinity Burial Ground in Kingston upon Hull. All three skeletons showed signs of delayed puberty and were slightly taller than average for their time, consistent with the genetic evidence showing extra X chromosomes.
These and other disorders of sex development (DSDs) can result in mixed or ambiguous sex-related physical characteristics, although those with milder forms "might not even be aware they have a DSD," they wrote. People with DSDs in the past likely lived according to conventional gender norms, and that seems to be the case with the aforementioned individuals, although none were buried with accompanying grave goods. However, the authors cited a 2022 study regarding a skeleton from early medieval Finland with possible Klinefelter syndrome who was buried with both masculine and feminine grave goods. And some Iron Age females have been found buried with "objects of power" that are usually buried with male individuals.
"Our method is also able to classify DNA contamination in many cases, and can help to analyse incomplete ancient DNA, so it could be applied to archaeological remains which have been difficult to analyze," said co-author Pontus Skoglund, who heads the Ancient Genomics Laboratory at the Crick. "Combining this data with burial context and possessions can allow for a historical perspective of how sex, gender and diversity were perceived in past societies. I hope this type of approach will be applied as the common resource of ancient DNA data continues to grow."
Communications Biology, 2024. DOI: 10.1038/s42003-023-05642-z (About DOIs).
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