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Comment by londons_explore | Hacker News Reader

Mice breed really fast - why does a mouse command a high price like that if you can make a new one for $10 in feed and 3 months?

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Adding to what josephpmay said, there's the issue of dealing genetic drift, so some groups have expensive-to-maintain systems to deal with that [0]. Which looks like restarting the line every 5 generations.

I have more experience with tissue culture than mice, but that's sounds surprisingly similar to passaging tissue cultures over and over [1]. Eventually you get to far out and have to start fresh, going back to stock cells.

[0] https://www.jax.org/jax-mice-and-services/find-and-order-jax...

[1] https://en.wikipedia.org/wiki/Immortalised_cell_line

Having to start over every 5 generations doesn't explain very much, though. Sure, you have to do some very expensive things to make a batch, but then four generations at a low 80 babies per female gives you two and a half million mice. So what are the other factors?

(Never maintained a mouse colony before and rgejman had some good points. I've never done an experiment that used male mice before, for example.)

Just some random expenses I could think of:

1) Maintaining the material to restart the line itself is pretty expensive. Expensive equipment, regular quality control, the scientists doing this maintaining would be relatively expensive. 2) The $17000 referenced in the article are "CRISPR/Cas9 injection to obtain knockout founders" I think?) are custom designed genetically modified mice to start a colony with [0]. More standard human disease-relevant db/db mice (model for diabetes) that I've used before are $500/mouse, as a reference. 3) More cynically, the labs that can actually make use of those $17000 CRISPR/Cas founder mice probably have a continuous flow of millions in funding, so they can charge whatever they want.

[0] https://www.jax.org/news-and-insights/jax-blog/2017/march/li...

> custom designed genetically modified mice to start a colony with

Ah, the idea that this is the price before amortizing across thousands of mice is perfectly reasonable.

I believe the mice used in a lot of research studies need to be genetically identical, so they need to be certain generation crosses

The expenses associated with animal husbandry at most research institutes raise the price to ~$1/day per cage of 5 mice.

So let's examine a setup with three cages, with two parent mice having a litter of 6 every 45 days. So every 45 days we have a new batch of 90-day-old mice, and they cost $135 or $23 each. Add a couple more dollars to sustain the ancestor mice, add enough inefficiencies to double the cost, that's still only $50 per mouse. Rearing costs aren't even going to hit 1% of $17000.

In practice you need to maintain large colonies in order to reliably have enough mice for experiments. Also you need to keep gender in mind because females can be housed together but males cannot and generally experiments are conducted in either one gender or the other.

So, let's say you need 20 female mice for an experiment (e.g. 4 groups of 5). That means that you need to have >40 offspring in order to get enough female offspring. That's at least 7 breeding pairs (assuming you're not harem breeding) and you've got to maintain them for 6-8 weeks until you can use them. That's >$1,000 in breeding costs before you get to the actual experiments.

But even after all that you're still at ">$50" per mouse. This isn't the part that makes a mouse cost 5 figures.

Transgenes can affect the fertility of mice or mess with their sexual behavior, it's not uncommon for transgenic lines to have erratic breeding schedules and reduced litter sizes compared to wild-type. Then if you get a litter, maternal care is very important. If a transgene messes up the mother's ability/drive to feed the pups, then they aren't going to make it very long (though you can foster/wet nurse them). Finally, depending on the required genetic profile, you may have a situation where only 50% or less of the offspring have the transgene of interest.

Some of this is "worst case scenario" stuff that wont apply to most lines. The real reason for the high price is mostly 1) that its expensive to make the transgenic mice in the first place and 2) demand is high enough that they can get away with charging that much.

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