Hello again! Welcome back to the LuxeSci Podcast, a podcast to re-ignite your wonder by exploring the intersection of science and luxury. I’m Dr. Lex, PhD, infectious disease expert, podcast host and a person who is eternally cold. For our third episode, I drew inspiration from the change in weather here in the Pacific Northwest. It’s gotten rainy and cold and all I want to do is to throw on something warm and cozy and curl up with a book and a cup of tea, predictable I know but a time-tested strategy for dealing with cold and dark. What is the pinnacle of cozy luxury, definitely cashmere. When I think of something warm and soft and wintery, it’s definitely cashmere. While cashmere has become more accessible over the years and yet is still synonymous with luxury. On this episode, I took a note from my brother who remarked that the last episode wasn’t really about the science of sequins so today we’ll dig deep into the genetic markers of cashmere and even delve into a little synthetic materials science. You’ve been warned
But first, some fun facts about cashmere:
In case you don’t know, cashmere is wool, specifically from goats
Cashmere comes from the soft undercoat of the goat, as opposed to the courser guard hair and is produced from the secondary hair follicle, which is different from mohair, which is produced by the primary and secondary hair follicle
Who knew there was a primary and secondary hair follicle in goats, certainly not me. This podcast has me going down rabbit holes so deep, I’m afraid I’ll bump into the Cheshire cat. I am continually learning more than I ever thought I would want to know about the topics we explore and that’s fascinating for me and I hope it is for you too
Back to cashmere fun facts: The wool is collected in the spring molting season and the softer hair separated from the courser hair and used to make cashmere items.
The name is thought to have originated from anglicanization of Kashmir (with a K), which is the name of a specific type of shawl introduced to Europe in the 19th century
Kashmir shawls have a specific Kashimir weave and are traditionally made from shahtoosh or pashmina wool
These shawls were originally designed for Indian men but have gained popularity all over the world and spawned the global cashmere trade
While cashmere can seem like a distinctly western material, it’s important to note that this product’s origin and deep history is in the Kashmir region of Asia, in addition to Afghanistan, Pakistan and India
Currently, China is the world’s biggest cashmere producer followed by Mongoli and then Afghanistan
Research
Since China is the world’s biggest cashmere producer, it makes sense that scientists there would be researching what drives cashmere production in goats
In fact, 20 breeds of goats from China yield 75% of the cashmere produced worldwide
Thus, optimizing goat breeding is of great economic importance as well as scientific interest
A research group led out of the Institute of Animal Sciences at the Chinese Academy of Agricultural Sciences in Beijing set out to study the biological characteristics of the genes that drive cashmere production
See – there is a method to my madness. Last episode we learned about genetic sequencing and this episode we’ll learn more about how sequencing is put to use in research
The research team compared the genetic sequences from Inner Mongolia and Liaoning Cashmere goats with non-cashmere Huanghuai goats.
Used the fixation index (Fst) – identify candidate genes between populations
The fixation index is a measure of population differentiation based on genetic structure – or in other words, using genetics to determine how related to animals are and when they differentiated from each other in an evolutionary tree
Using fst and other techniques – the team identified two genes, WNT10A and CSN3 as having potential biological functions related to cashmere traits
SNPs were identified by high FST and XP-EHH values = 18 SNPs with 20 genes.
SNPs stands for single nucleotide polymorphisms and while that’s a long name, it’s a short concept. SNPs are single nucleotide (or base, remember from last time, the A, T, G, C that make up DNA) that is different between chromosomes in a population. So in a certain part of the DNA, I can have a A and you can have a G
Genes that overlapped between the two approaches were defined as candidate genes with strong selection signatures.
Gene pathway analysis (comparing to other function of these genes in other species, mostly mice because you can knock-out the gene in lab mice and determine the effect) identified potential modes of action of these two genes:
WNT – signaling molecule that is a regulator during hair follicle initiation, morphogenesis and development (found humans and mice as well)
CSN3 – may be involved in regular hair follicle development but remains to be verified and researched further
A note on genetic pathway analysis – it’s not possible or usually ethical to get rid of a gene (knock-out) or add one in (knock-in) in most animal species. One major exception is mice bred for laboratory research. Knocking out or knocking in genes to lab mice has led to huge advancements in our understanding of gene expression and how genes and their products interact. This is one way to discover what a gene may be doing in an animal, refer to the mouse data.
While it might not seem on the surface that we have much in common genetically with a mouse or a mouse to a goat, nature likes to use the same systems so there are many genes that have the same or similar functions across species
The researchers identified additional genes related to hair growth including PAD12, which belongs to a group of genes responsible for forming the major amino acid in the inner root sheath and a portion of the hair follicle, FOXP1, which regulates hair follicle stem cells and others
Recap – researchers sequenced the genomes of several breeds of goats and then performed comparisons to see the differences in the presence or abundance of the genes to see what genes are specific to cashmere production. They did this by identifying common genes in the cashmere goats and then comparing those genes to what is know about those genes in other species (i.e mice) to get an idea of how the genes could be functioning in the goats
They also looked at the genetic evolution of these traits to see when species may have diverged or when intentional breeding may have changed the genetic makeup of the goats.
Research such as this allows farmers to select for the best cashmere in their flocks and breed for those traits. So, sort of akin to GMOs but without the in laboratory genetic manipulation.
Fun side fact – did you know that genetics was discovered by a monk while cross-breeding pea plants. Mendel noticed that certain plants produced certain traits when bred with each other and he painstakingly worked what we call Mendelian genetics, which is about what genes will dominate or not when mixed together. So essentially, we’ve had genetically modified organisms for centuries, perhaps millennia
So that’s a little about the genetics of cashmere wool but what about the fiber itself.
I found an article in the journal Molecules (what a great name, right) looking at the structure and properties of modified cashmere fibers
Cashmere fiber has some excellent properties that make it so sought after. Cashmere is versatile, light, soft, flexible and has reasonable moisture absorption.
However, the structure and chemical components of cashmere (which differ from other wools) lead to some drawbacks. I think we’re all familiar with these, like the easy shrinkability of cashmere and how it doesn’t really wear great. Additionally, when knitted into fabric, cashmere fibers can absorb dust, sweat, bacteria, etc from environment (gross!), which accelerates the degradation of the cashmere fibers
Industry practice is to treat the surface of the fiber to overcome these limitations
This treatment can be done a number of ways, including plasma or ultrasonic treatment, changing the structure, using chemical reagents
Plasma irradiation intrigued me. It sounds like something out of a science fiction movie but is instead my scientific nemesis, physics. Plasma can be considered a fourth state of matter alongside solid, liquid and gas. Plasma happens when atoms in a gas become ionized resulting in a substance with equal numbers of positively and negatively charged particles. It can be produced in a lab by heating gas to extremely high temperatures. Pretty nifty and apparently it can be used a pre-treatment for cashmere. That’s some space age materials work right there.
The team of researchers in the paper in the August 2020 edition of Molecules (Led by Jifeng Li of the College of Light-Textile Engineering and Art at Anhui Agricultural University) thought that there could be a better alternative for cashmere treatment using chitosan
Chitosan (linear polysaccharide [sugar]) is found in chitin (exoskeleton of arthropods [bugs and crustaceans] and cell walls of fungi) and is non-toxic and has good antibacterial activity. They are currently used in the biomedicial field as an antibiotic on items such as artificial skin, scaffolds and matrices
Currently the process of treating cashmere with chitosan involves chemical cross-linking agents, plasma irradiation or partial carboxymethylation – none of which are ideal from a manufacturing stand point
Li et al developed a method to oxidize chitosan, thus creating the opportunity to graft the chitosan on to the cashmere via a reaction between the chitosan and the amino acids in the cashmere fiber.
oxidation - loss of electrons from a molecule, which leads to a charged molecule (ion!)
this loss of electrons from the chitosan cause it to want to bond to another molecule to get itself back to a neutral charge. in this example, the chitosan bonds to the amino acids in the cashmere, thus coating the cashmere with chitosan
After the cashmere grafting the resulting fibers had antibacterial properties against S. aureus and E. coli and displayed increased crease resistance and moisture regain
So for our recap – we learned that hair follicle growth in the secondary follicle of cashmere goats is driven by a complex genetic pathway that includes genes such as CSN3 and WNT10a. we also explored how cashmere fibers compare to other wool and how it is treated to overcome some of its deficiencies.
Now all is not perfect in the world of cashmere. One of my good friends asked me to also explore the environmental aspects of applicable podcast topics and this one was ripe for it.
According to a Harpers Bazaar article from 2020, cashmere makes up $4 billion of the $60 billion luxury market
The accelerated advance of so-called fast fashion has meant an increased demand for cashmere globally.
With most of the cashmere coming from Mongolia and China and since goats are grazing animals, this can have a huge environmental impact
To illustrate, 90% of Mongolia is deemed fragile dry land prone to desertification according to the United Nations Development Programme and grazing animals can quickly use up land resources. With cashmere goats eating ~10% of their body weight in grass a day and eating close to the roots and destroying the plants, they have significantly contributed to this desertification
the growing demand for cashmere has led to increase demand for grazing land for the goats and more natural environment degradation
The National Resource Defense Council recommends minimizing cashmere until more sustainable practices can be developed
So what’s a seeker of soft, cozy items to do, I wouldn’t really recommend synthetic fibers necessarily but there are sustainably cashmere outfitters out there
Glossary
SNP – single nucleotide polymorphism – one nucleotide difference between individuals
Plasma – state of matter that consists of a gas of ions (charged particles)
oxidation - loss of electrons from a molecule
Polysaccharide - sugar
Thanks for listening to this episode of LuxeSci. A very special thank you to my audio engineer, Dimos. Our theme music is Harlequin Moon by Burdy. If you have a correction, comment or praises, you can reach me at: drlex@luxesci.com. We’re on Twitter and Instagram at luxescipod and our website is luxesci.podcastpage.io. If you like us, please subscribe. Please also leave us a review where ever you listen to podcasts. See you again in 2 weeks!
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