Developmental myosins: expression patterns and functional significance

Skeletal Muscle

Table 1 MYH and MYL genes expressed in developing mammalian skeletal muscle

Protein	Gene	Expression in developing muscle	Expression in adult muscle
Myosin heavy chains^a
MyHC-emb	MYH3	Embryonic and fetal muscle	Specialized muscles^b
MyHC-neo	MYH8	Embryonic and fetal muscle	Specialized muscles^b
MyHC-slow	MYH7	Embryonic and fetal muscle	Type 1 muscle fibers and ventricles
MyHC-2A	MYH2	Fetal (human) or early postnatal (mouse) muscle	Type 2A muscle fibers
MyHC-2X	MYH1	Late fetal (human) or early postnatal (mouse) muscle	Type 2X muscle fibers
MyHC-2B	MYH4	Postnatal muscle	Type 2B muscle fibers
Essential myosin light chains^c
MLC-1fast^d	MYL1	Embryonic muscle	Fast muscle
MLC-3fast^d	MYL1	Fetal muscle (mouse: after E15)	Fast muscle (2B > 2A)
MLC-1emb/atrial	MYL4	Embryonic muscle, heart	Atria
MLC-1sb	MYL3	Fetal muscle (mouse: after E15)	Slow skeletal muscle and ventricles
MLC1-sa	MYL6B	Fetal muscle (human)	Slow skeletal muscle, not ventricles, in human, not mouse
Regulatory myosin light chains
MLC-2fast	MYLPF	Embryonic and fetal muscle	Fast muscle
MLC-2slow	MYL2	Embryonic and fetal muscle	Slow muscle and ventricles

^aOther five MyHCs coded by genes with limited expression in specialized skeletal muscles (MYH6, MYH7b, MYH13, MYH15, and MYH16) are not considered in this Table (see [1])
^bExtraocular, masticatory, laryngeal muscles, and muscle spindles
^cAn additional MLC, coded by the MYL6 gene, which is normally expressed in smooth muscle and non-muscle cells, is detectable in human fetal muscle and human cultured muscle cells [50]. However, it is not clear whether this MLC is associated to sarcomeric myosins
^dSplicing product of the MYL1 gene

ISSN: 2044-5040