Recombinant Rat Transmembrane protein 216 (Tmem216)

Introduction to Recombinant Rat Tmem216

Recombinant Rat Transmembrane protein 216 (Tmem216) is a laboratory-produced version of the naturally occurring Tmem216 protein found in Rattus norvegicus. This protein is part of the tetraspan transmembrane protein family and is primarily localized in the ciliary transition zone. The recombinant form is synthesized through various expression systems to enable detailed scientific study and applications . Mutations in the TMEM216 gene have been linked to serious human disorders, including Joubert syndrome and Meckel syndrome, which involve photoreceptor degeneration among other pathologies .

The full-length rat Tmem216 protein consists of 141 amino acids forming a transmembrane structure with multiple membrane-spanning domains. The protein sequence is: MAPRDKRLSSTPLEILFFLNGWYYATYFLLELLIFLYKGLLLPYPTANLVLDVVMLLLYLGIEVIRLFFGTKGNLCQRKMPLGISVALTFPSAMMASYYLLLQTYVLRLEAIMNSILLFFCGSELLLEMLTLATFSSMDRI . This sequence determines the protein's structure and function, enabling its role in ciliary transitions and cellular signaling.

Protein Identification and Classification

Recombinant Rat Tmem216 is identified through several standard database references that enable consistent identification across research platforms:

The protein belongs to a family of transmembrane proteins that span the cellular membrane multiple times. As a tetraspan protein, Tmem216 traverses the cell membrane four times, creating both intracellular and extracellular domains that facilitate its function in the ciliary transition zone .

Expression Systems

Recombinant Rat Tmem216 can be produced through various expression systems, each offering different advantages for protein quality, yield, and post-translational modifications:

The choice of expression system depends on the specific research requirements, with mammalian cell-derived proteins often preferred for functional studies due to their closer resemblance to the naturally occurring protein.

Stability and Handling Precautions

Liquid forms typically maintain stability for approximately 6 months at -20°C/-80°C, while lyophilized forms can remain stable for up to 12 months at the same temperatures . To maintain protein integrity, repeated freeze-thaw cycles should be avoided, as they can lead to protein denaturation and loss of activity . For reconstitution of lyophilized proteins, manufacturers often provide specific buffer recommendations to ensure optimal protein stability and function.

Tissue Expression

Research on Tmem216 expression patterns reveals its presence in multiple rat tissues:

Within the retina specifically, Tmem216 expression has been observed in the outer nuclear layer, inner nuclear layer, and ganglion cell layer, suggesting important functions throughout the visual system . Expression begins early in development and continues into adulthood, indicating roles in both developmental processes and tissue maintenance.

Cellular Function

Tmem216 functions primarily as a component of the ciliary transition zone, which serves as a gateway controlling protein entry and exit from the cilium. Studies using knockout models have demonstrated several critical functions:

1. Regulation of photoreceptor outer segment formation and maintenance

2. Control of protein transport within ciliated cells

3. Support of normal disc morphology in photoreceptor outer segments

4. Maintenance of ciliary axoneme structure

These functions highlight Tmem216's role as a crucial regulator of ciliary structure and function, particularly in specialized cells like photoreceptors.

Role in Photoreceptor Function

Research using zebrafish models with TMEM216 deletion has provided significant insights into the protein's function in photoreceptors. Knockout of tmem216 results in:

1. Reduced immunoreactivity to rod photoreceptor outer segment markers

2. Decreased immunoreactivity to cone photoreceptor outer segment markers

3. Increased cell death (TUNEL-positive nuclei) in photoreceptors

4. Shortened photoreceptor ciliary axonemes

5. Mislocalization of outer segment proteins (rhodopsin, GNAT2, red opsin)

6. Abnormal disc morphology in photoreceptor outer segments, including shortened discs and vesicles/vacuoles

These findings demonstrate that Tmem216 is essential for normal photoreceptor development, function, and survival.

Disease Association

Mutations in the human TMEM216 gene are associated with two related disorders:

1. Joubert Syndrome: A genetic disorder characterized by retinal dystrophy, cerebellar ataxia, oculomotor apraxia, hypotonia, neonatal breathing abnormalities, psychomotor delay, and renal disease. Neuroimaging reveals the diagnostic "molar tooth sign" resulting from cerebellar vermis abnormalities .

2. Meckel Syndrome: A more severe disorder often resulting in embryonic or perinatal lethality, with additional manifestations including occipital encephalocele, polycystic kidneys, polydactyly, and liver fibrosis .

The investigation of Recombinant Rat Tmem216 provides a valuable tool for understanding the molecular mechanisms underlying these disorders and potentially developing therapeutic approaches.