Table 1 Summarized alterations in fatty acyl chain length and saturation in unbound and protein-bound epidermal lipids in Fatp4^−/− mice.

	Fraction number	Lipid class	Acyl chain length^a	Changes in Fatp4^−/−
				Saturated		Unsaturated
				≥C25	<C25	≥C25	<C25
Unbound FAs	4 & 5	NHFA	C14-C34	≅	↑^e	↑	↑^e
		AHFA	C18-C26	?	↑	n.a.	varied
		BHFA	C26	?	n.a.	n.a.	n.a.
		OHFA	C30-C36	↓	n.a.	↑^e	n.a.
		OAHFA	C30-C36	↓	n.a.	↑^e	n.a.
Unbound lipids	3	Cer(NS)	C16-C32	↓	↑	↑^e	↑^e
		Cer(NdS)	C24-C26	↓	↓	n.a.	n.a.
		Cer(NP)	C22-C26	≅	↑	n.a.	n.a.
		Cer(AS)	C16-C28	?	↑^d	↑	↑
		Cer(AdS)	C16, C27, C28	n.a.	≅	?	n.a.
		Cer(BS)	C26	↓^c	n.a.	n.a.	n.a.
		Cer(OS)	C32-C36	↓	n.a.	↑^e	n.a.
		Cer(EOS)	C30-C36	↓	n.a.	↓	n.a.
	6	GlcCer(NS)	C16-C28	↓	≅	↑	≅
		GlcCer(NdS)	C24-C26	↓	↓	n.a.	n.a.
		GlcCer(NP)	C22-C26	↓	≅	n.a.	n.a.
		GlcCer(AS)	C16-C28	?	↑^d	↑	↑
		GlcCer(AdS)	C16, C27, C28	n.a.	↓	?	n.a.
		GlcCer(BS)	C26	?	n.a.	n.a.	n.a.
		GlcCer(OS)	C32-C36	↓	n.a.	↓^e	n.a.
		GlcCer(EOS)	C30-C36	↓	n.a.	↓	n.a.
	2	1-O-Cer(ENS)	C16-C28; C16-C26^b	↓	↑^e	↑^e	↑
	3	MAG	C22-C30	↓	↓	n.a.	n.a.
Protein-bound FAs	4 & 5	OHFA	C32-C36	n.a	n.a	↓	n.a
Protein-bound lipids	3	Cer(OS)	C28-C36	↓	n.a.	varied	n.a.

Fractionated unbound and protein-bound epidermal lipids of newborn mice were analyzed by ESI-MS and quantified as described in Materials and Methods. Changes in lipid abundance in Fatp4^−/− mice compared to controls were summarized in 4 categories based on the chain length (≥C25 or <C25) and saturation (saturated or unsaturated) of the fatty acyl chains. 1-O-Cer(ENS) species that carry two saturated acyl chains are categorized as saturated whereas those that carry one or two unsaturated acyl chains are categorized as unsaturated. ^aamide-linked acyl chain or acyl backbone; ^b1-O-linked acyl chain; ^cassessed by TLC; ^dnot for C16; ^enot for all species; ↑ and ↓, abundance significantly increased or decreased, respectively, compared to controls; ≅, abundance unchanged compared to controls; ?, abundance unknown; n.a., non-applicable.

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