Table 4. Ion transporters and channels expressed in vivo, but not detected in culture.

Apical membrane	Basal membrane	Unknown polarity
Like Na+, K+, 2Cl- cotransporter (splice isoform A)	Like Na+ conductance (voltage-gated, type 8)	ATP2B1, Ca2+-ATPase
*KCNJ3, K+-inwardly rectifying channel	L-type Ca2+ Channel	NDCBE1, Na+-driven Cl−HCO3 exchanger
*KCNJ5, K+-inwardly rectifying channel	CACNA1B, L-type Ca2+ Channel	KCND2, K+-voltage-gated channel
KCNA4, K+-voltage-gated channel	CACNA1C, L-type Ca2+ Channel	TASK2, volume-sensitive K+-channel
KCNC1, K+-voltage-gated channel	CACNB4, Ca2+ Channel	KCNC1, K+-voltage-gated channel
SLC24A2, Na+/K+/Ca2+ exchanger		*TALK-1, K+- channel
		SLC16A5, moncarboxylic transporter

For every cohort of genes described in this study, there were examples of genes that were expressed in vivo but not in culture. By far, ion transporters where the cohort that had the highest percentage of genes that cultured cells failed to express. Strikingly, most of these were potassium and calcium channels. The asterisk represents undetected in E14 cultures only.