[Scientists reported an assortment of findings
resulting from a sweeping and novel analysis of data from the prenatal tests of
141,431 participants]
By Steph Yin
 |
People of the Miao ethnic minority in Guizhou province, southwestern China.
A sweeping study of Chinese DNA had more than 140,000 participants,
representing nearly every Chinese province and 37 out of 56
officially recognized ethnic groups. Credit Agence
France-Presse — Getty Images
|
Lamb stew, hearty and fragrant, cooked until
meat falls off the bone and served alongside thick, chewy noodles — this is the
type of food that cuts through northern China’s winter chill.
Further south, warmer climates support more
crops. Fresh, stir‐fried greens
might accompany dim sum in Guangdong or punctuate a spicy meal in Sichuan.
Lychee, durian and other fruits ripen the air.
Comb through the DNA of Chinese people and
you’ll find a trace of this culinary story, according to the largest‐scale genetic study of Chinese people to date, published Thursday in Cell. The authors reported that a mutation of
FADS2, a gene involved in metabolizing fatty acids, is more common in northern
than southern populations, indicating a diet richer in animal content. It is
one of an assortment of findings resulting from a sweeping analysis of genetic
information from 141,431 participants.
The approach — a novel one using data from
prenatal blood tests — came with a trade‐off.
Though researchers were able to cheaply sequence a large number of genomes,
they had access to a small fraction of each person’s genome, much less than
what genome‐wide studies
typically look at.
Nevertheless, the study suggests that simple
clinical tests can be an effective resource for surveying the genetics of large
populations and generating hypotheses for study, said Ekta Khurana, an
assistant professor of computational genomics at Weill Cornell Medicine in New
York who was not involved in the research.
“This can be expanded to include not just
mothers, but all different people,” she said.
The authors used data from noninvasive
prenatal testing for fetal trisomy, a condition that can cause Down syndrome.
Pioneered in China, the test analyzes free‐floating
bits of fetal DNA in the mother’s blood and is administered for $100 or less
throughout the country, said Xin Jin, aresearch scientist at BGI, a genome
sequencing firm in Shenzhen, and an author of the paper. High‐quality, whole genome sequencing, in
comparison, costs about $1,000 per person.
The data set, which represented nearly every
Chinese province and 37 out of 56 officially recognized ethnic groups, eclipsed
many genome‐wide
studies, which often include only thousands, or tens of thousands, of
participants.
But the team’s analysis covered a mere 10
percent or less of each person’s genome, while most rigorous genome‐wide studies cover 80 percent or more, said
Anders Albrechtsen, an associate professor at the University of Copenhagen and
an author of the study.
To overcome this, the researchers relied on
heavy computation and statistics, designing custom software that could infer
missing DNA. They reported many preliminary but interesting insights.
For instance, the Han — comprising 92 percent
of China’s population — were quite genetically homogeneous, mostly differing
between the North and South.
This likely reflects governmental policies
and job opportunities since 1949, which have largely driven migration eastward
or westward, said Siyang Liu, a senior research scientist at BGI and lead
author of the paper.
Her team identified several gene variants
differing in frequency between northern and southern populations, related to
immune response, bipolar disorder and earwax type.
Minority ethnic groups showed more genetic
divergence than the Han, particularly Uyghurs and Kazakhs in Xinjiang and
Mongols in Inner Mongolia.
This is noteworthy because sequencing studies
are rarely done on ethnic minorities, even though findings can have important
medical implications, said Charleston Chiang, an assistant professor at the
University of Southern California’s Keck School of Medicine who was not
involved in the research.
The researchers also diagnosed viruses in the
mothers’ blood by checking DNA that did not align to the human genome against a
database of viral sequences. They found a relatively high prevalence of
hepatitis B and other viruses that can affect pregnancies, as well as a gene
variant associated with roseola, which causes a high fever and rash in babies.
Last, to show that noninvasive pregnancy
testing data can reveal associations between genes and specific traits, the
scientists analyzed height and body mass index across their sample, finding 48
gene variants associated with height and 13 with body mass index. They also
reported gene variants associated with maternal age and the likelihood of
having twins.
Some of these associations had been reported
in previous studies with Europeans, but the team also discovered new links,
which underscores the importance of doing research in non‐European populations, Dr. Jin said.
This study served as proof‐of‐concept,
he added. His team is moving forward on evaluating prenatal testing data from
more than 3.5 million Chinese people.
Earlier reporting on genetic studies