Fig. 1: Phenotypic and dysmorphic features of patient 1 (A and B),...
This Misunderstood Genetic Condition Has Afflicted Humans For Centuries ...
Beneath the shadow of an ancient hilltop village of Alto de la Cruz situated in Spain's northern Navarre region, an infant was buried with all the pomp and finery not typically reserved for anyone in this region during the Iron Age. While the dead were usually cremated, this baby was placed beneath a dwelling surrounded by sheep and goat remains — likely offerings for the afterlife — bronze rings and a Mediterranean sea shell.
This infant, whose remains date back to nearly 800 to 500 B.C., wasn't the only one laid to eternal rest with such tender care. Since the 1940s, archaeologists have uncovered infants elsewhere in Spain, Greece, and Bulgaria buried in a similar reverent fashion. But only now, with the help of genetic sequencing, are scientists uncovering what exactly was so special about these children.
In a study published this week in the journal Nature Communications, a group of scientists found the baby of Alto de la Cruz and five other infant skeletons analyzed out of nearly 10,000 ancient remains had a condition familiar to us in the modern world: Down syndrome. Another skeleton of an infant girl also discovered in Alto de la Cruz had a different chromosomal condition known as Edwards syndrome.
"It will always continue to shock and surprise me how different yet similar we have been," Adam Rohrlach, the paper's first author and a statistician at the Max Planck Institute for Evolutionary Anthropology and the University of Adelaide in Australia, tells Inverse. "It's nice to know in our past, we absolutely loved everyone that we could have with respect to [Down Syndrome]. Babies were loved and in no case were they mistreated, in no case were they buried differently."
Down and Edwards syndromes belong to a class of chromosomal abnormalities called trisomies, where a pair of chromosomes — humans have 23 pairs for a total of 46 chromosomes — get an extra third. This tends to happen when, during cell division (either the mother's egg, father's sperm, or after fertilization), chromosomes are split unevenly such that a cell gets an extra copy instead of just a single chromosome. In the case of Down syndrome, there's one extra copy of chromosome 21; in Edwards syndrome, it's an extra copy of chromosome 18.
Remains of individual "CRU001" who was discovered in Alto de la Cruz. This baby boy had Down syndrome and was estimated to have been around 38 weeks gestation at his time of death.
Government of Navarre and J.L. Larrion.For the most part, trisomies are lethal. Most babies born with Trisomy 18 die before they're born, and any who reach term won't make it past their first year of life. The odds are better for Trisomy 21 (aka Down syndrome) with advanced medical interventions that can significantly improve quality of life and life expectancy. However, thousands of years ago, anyone born with a trisomy wouldn't have survived.
While some studies suggest prehistoric societies like in northern Peru or modern-day Hungary cared for disabled individuals within the community, it's been challenging to peer into the archaeological record to say anything about trisomy, such as its prevalence in ancient times and potentially what life was like for such babies born, says Rohrlach.
In the new study, Rohrlach and his colleagues examined an archaeological library consisting of over 9,800 human skeletal remains collected from the last several decades. These human remains come from all over the world, but a majority of them hail from Europe. Some skeletons date as far back as the Paleolithic Period, or Stone Age, as old as 45,000 years ago; other remains are more contemporary within the last century.
To find which skeletons had a chromosomal abnormality, the researchers did shotgun sequencing, a method of sequencing DNA that doesn't focus on a specific part of the genome but quickly scans random bits from bones, teeth, or other organic remains. This is particularly useful for ancient DNA, which is often highly degraded and fragmented. Trisomy also tends to be easy to spot because you have that whole extra chromosome.
Rohrlach and his colleagues found seven cases of trisomy associated with infant skeletons ranging in age from as young as 26 weeks (meaning it died before birth) to six months of age. Six of the babies had Down Syndrome: three infants from Iron Age Spain, a girl from Greece dating back to the Bronze Age, a 16th-century infant from Finland, another infant from Stone Age Ireland, and a six-month-old girl from Bulgaria. An infant with Edwards syndrome who likely died at term was also found in Alto de la Cruz.
Artistic rendition of Las Eretas, an archaeological site that was once a proto-urban center in Early Iron Age Navarra, Spain. One infant skeleton with Down syndrome was uncovered at this site.
Iñaki Diéguez/Javier Armendáriz.Considering most of the babies were buried within dwellings — especially in Iron Age Spain, where cremations were likely the norm — and with grave goods like fine jewelry (the infant from Greece was found adorned with a beautifully colored necklace made of glass, faience, and carnelian beads), the researchers believe their burials reflected the love their parents or immediate community had for them.
Another component of the study was to see if it was possible to see whether genetic conditions like Down syndrome could be identified just by looking at the bones themselves. For example, with Down syndrome, vitamin deficiencies can impact bone density and shape, the latter especially visible to the naked eye.
The skeletons did exhibit abnormalities consistent with Down and Edwards syndrome, such as poor bone density; one skeleton had a bit of bone protruding from his skull, which the researchers don't believe was the result of any violence inflicted on the child. But Rohrlach cautions it's hard to say for sure what's associated with the condition or with the mother's health impacting fetal development.
While the study did find the prevalence of Down and Edwards syndrome in ancient times was as rare as it is today, the biased sampling makes it difficult to definitively conclude how rare such pregnancies were.
Rohrlach hopes future research will unlock more insight into the lives of those whose stories aren't often told.
"These are people that either had a lived experience, or their experience was short but certainly influenced the people around them," he says. "Parents know what it's like to lose a child and that can't be a modern phenomenon. So to not report on that part of it, to not look into how they were buried and how they were loved — and maybe even the negative side, maybe how they were mistreated, which we, fortunately, didn't observe — that's just as important as the genetic results."
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Down Syndrome, Edwards Syndrome Found In Ancient Individuals
Researchers have reported chromosomal disorders discovered from prehistoric skeletal remains, dating up to approximately 5,500 years old — including six cases of Down syndrome and one case of Edwards syndrome. According to the authors of a paper published in the journal Nature Communications, the findings may represent the first time Edwards syndrome has been identified from historic or prehistoric remains.
Individuals with chromosomal trisomy carry three copies of a chromosome in their cells, instead of two. Trisomy of chromosomes number 21 or 18 result in Down syndrome and Edwards syndrome, respectively. There have only been a few documented cases of Down syndrome in ancient individuals, largely owing to difficulties in identifying genetic disorders without modern techniques for analysing ancient DNA samples. How certain ancient societies were affected by and responded to genetic disorders remains elusive.
Dr.Adam Rohrlach from the Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany and others screened almost 10,000 genomes from ancient human skeletal remains from either Ireland, Bulgaria, Greece, Spain or Finland for chromosomal trisomies and identified six cases of Down syndrome and one case of Edwards syndrome. These individuals, who mostly died either before or shortly after birth. Some of the cases were particularly ancient; two were from as far back as the Bronze Age (about 2,700 BCE) and one from the Neolithic period (about 3,500 BCE).
"When skeletal preservation and completeness was sufficient, we record all observed pathological lesions, and match these to osteological markers which are consistent with a diagnosis of the trisomy," they write.
"Three cases of trisomy 21 [Down syndrome], and the case of trisomy 18 [Edwards syndrome] were detected in two contemporaneous sites in early Iron Age Spain (800-400 BCE), potentially suggesting a higher frequency of burials of trisomy carriers in those societies," they write.
The authors note that all individuals appear to have been cared for after death through various rituals indicating recognition of them as part of their communities, and in a few cases were given exceptional burials or elaborate grave goods. For example, the individual buried in Early Iron Age Navarra, Spain, was buried with bronze rings, a Mediterranean seashell, and surrounded by the remains of three sheep and/or goats. The findings offer some perspective into the way that these conditions were recognised among past communities.
Published - February 24, 2024 09:10 pm IST
Robertsonian Translocation: All You Need To Know - WebMD
Abnormalities in the structure of chromosomes within someone's genetic makeup are called structural chromosomal abnormalities.
Robertsonian translocations are very rare structural chromosomal abnormalities — with only about one in 900 people having them. Translocations like this happen on their own and are out of our medical control.
If the Robertsonian translocation is passed along to a child, it may cause a type of Down syndrome. There is also a risk of having a baby with Patau syndrome, a rare genetic condition that causes serious birth defects.
Chromosomes are the microscopic building blocks of our genetic makeup. They tell your body all of the information it needs to know in order to take shape and function properly.
Humans normally have 46 chromosomes — 23 from the mother and 23 from the father. Each chromosome has a short and a long arm.
Chromosomes 13, 14, 15, 21, and 22 have a very short arm, which doesn't contain any unique genetic material, and are called acrocentric chromosomes.
In a translocation, two of these five chromosomes break at the short arm. The broken acrocentric chromosomes then fuse together so that these chromosomes now have two long arms but no short arms. While the short arms on these chromosomes aren't functional, the short arms on the remaining acrocentric chromosomes can be of service.
Because the other acrocentric chromosomes lend only their short arms, there are no health problems that come from Robertsonian translocations. Still, a Robertsonian translocation carrier will only have 45 chromosomes, not 46.
You may either inherit a Robertsonian translocation from your parents or get it over time. So, you can also pass it along to your child.
There are two kinds of Robertsonian translocations:
The main medical concern for people who have a Robertsonian translocation is that they may pass along extra genetic material to their children. But, your child won't always inherit your translocation.
The inheritance of a Robertsonian translocation from you to your child can work out in three ways:
A woman with a Robertsonian translocation has a high risk of miscarriage or having a child with a disability. But, the miscarriage risk is pretty low in Robertsonian translocation carriers.
Some men with a Robertsonian translocation have lowered sperm count — or a lessened ability to produce sperm.
Most people might not even know that they have a Robertsonian translocation until they have a baby born with extra genetic material. However, there are tests that both you and your partner can take to get a better idea of the risk your child might have of having a disability.
This test is usually recommended to people who have been known to have chromosome translocations in their family or to people who are at risk of having chromosomal irregularity.
The test will be a simple blood test — where your blood is drawn and the chromosomes in your blood cells are seen under a microscope. Your healthcare provider checks to see if your chromosomes are regular or not.
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