Thread by @FondOfBeetles

On the exclusion of people with DSDs from the standard model of sex.

A thread. 1/

As a developmental biologist, I study what various proteins do during development of an embryo. One of the most powerful tools I can employ is the study of how embryos develop in the absence of a specific protein (“knockout experiments”). 2/

If one can observe, as in my own research, that when Protein X is absent during development, pelvic nerves do not grow properly, we can conclude that Protein X is necessary in some way for pelvic nerves to grow properly. 3/

I may then go on to study how Protein X is necessary. What is its function in pelvic nerve growth? Does it maybe regulate lengthening of nerves? Perhaps it controls the path they take? And so on, testing various possibilities. 4/

And after such research, we add Protein X (and any known function) to our current model of pelvic nerve growth. Our understanding of this process has improved and we have a fuller picture of how pelvic nerves grow. 5/

We have come to understand more about pelvic nerve growth by studying an embryo where pelvic nerve growth has deviated from a healthy state. And the original embryo model for my mini research programme?

Humans. 6/

Babies born with Disorder X have symptoms that suggested a nerve defect of some kind. We found out that babies with Disorder X are missing Protein X by analysing their DNA and finding mutations in Gene X that mean it can no longer code for the production of Protein X. 7/

Until we studied babies with Disorder X, we had no idea that Protein X was involved in pelvic nerve growth. In fact, although scientists knew Protein X was present in the early embryo, nobody had any clue of what its function was. 8/

And without that study of babies with Disorder X, our model of pelvic nerve growth would be (more) incomplete than it is today. To be sure, babies with Disorder X have been irreplaceable in developing our current model of pelvic nerve growth. 9/

And the same principles are of course true for many other human disorders, diseases or variations from healthy state, including those related to sex development (collectively, DSDs). 10/

Just as for babies with Disease X, who have been essential to our model of how pelvic nerves grow, understanding DSDs has been essential to our model of how sex is determined, how it differentiates and how it develops. 11/

For example, we did not know that a protein called RSPO1 was part of our model of sex development until mutations in the RSPO1 gene were identified in XX patients with ovarian failure/”sex reversal”.

nature.com/articles/ng1907 12/

The role of RSPO1 in suppressing differentiation of male gonads (testes) is a subject of much research. Scientists now understand to some extent how RSPO1 function slots into our model of sex development. 13/

To suggest that people with DSDs, from whom we have learned so much about sex development, are actually best represented (read: othered) by some alternative model seems, well, a little impolite at best. 14/

People with DSDs are not simply “understood within a binary model”, the threads of their exceptional molecular and anatomical variations are woven into the very fabric of the model.

End/