picture: Picture from Milne CA et al. (1999) Curr Biol "ETR-1, a homologue of a protein linked to myotonic dystrophy, is essential for ...."

Figure 1. Expression pattern of etr-1. GFP fluorescence pattern of animals carrying a rol-6 marker and a non-integrated extrachromosomal array of a GFP-lacZ reporter (derived from plasmid pD96.04, a gift from A. Fire) fused to promoter elements of etr-1. In early embryos, muscle cells are initially seen as a continuous sheet on the lateral side of the embryo. Between 300 and 350 min, starting from the anterior, the sheet begins to separate as the cells move to form two dorsal and two ventral muscle quadrants. (a,b) Dorsolateral view of GFP expression in an approximately 300 min embryo is seen in a muscle sheet which is just beginning to separate at the anterior. (c,d) 1.5-fold-stage embryos (approximately 430 min) express GFP in the four muscle quadrants along the length of the embryo (two of which are seen clearly in this example). (e) Adult animals show expression in body-wall muscle, seen here in stripes along the length of the adult hermaphrodite. The four muscle quadrants spiral along the length of the animal because of the presence of the rol-6 marker. Anterior is to the left. (f,g) Ventral view of vulval muscle. (h,i) Intestinal muscle seen in lateral view with the ventral side to the left. (j,k) Lateral view of anal sphincter muscle (arrowhead) with dorsal at the top. (b,d,g,i,k) The corresponding Nomarski images of the fluorescence images shown in (a,c,f,h,j).

paper:

Milne CA et al. (1995) International C. elegans Meeting "A CANDIDATE PRIMARY SEX DETERMINATION LOCUS ON THE X CHROMOSOME, fox-1"

Milne CA, Hodgkin JA, Skipper M

[International C. elegans Meeting, 1995]

Sex in C. elegans is determined by the ratio of X chromosomes to autosomes (X:A ratio), such that 2X:2A animals are hermaphrodite and 1X:2A animals are male. This primary signal is required to set the state of both sex determination and dosage compensation. It is not known how the X:A ratio is assessed, or how many sites contribute to the numerator (X) and denominator (A) components of this ratio. A dose-sensitive region near the left end of the X chromosome was identified by X chromosome duplications and subsequently by testing individual cosmids from this region. Increasing the copy number of certain of these cosmids has feminizing and lethal effects on XO animals. The lethality arises from improper dosage compensation. These cosmids define fox-1 (Feminizing locus On the X), which appears to act as a major numerator site (Hodgkin et al., Development 120: 3681, 1994). A 1.7 kb embryonic cDNA from this region was found to encode a protein containing an RNA-binding motif. Further investigation of this transcript indicates that it is trans- spliced to an SL1 leader sequence. Developmental northern blot analysis indicates that two related transcripts are detectable at early stages, one at 1.8 kb (corresponding to the cDNA) and a less abundant species at 2.4 kb. In mid-larval stages these transcripts are not detectable, and in adults only the 1.8 kb transcript is seen. Direct tests of the role of these transcripts in generating the Fox-1 phenotype are in progress, as well as genetic and molecular experiments directed at disrupting fox-1, in order to explore what other functions it may have.

paper:

Milne CA et al. (1998) European Worm Meeting "FURTHER ANALYSIS OF FOX-1, AN RNA-BINDING PROTEIN INVOLVED IN THE PRIMARY SEX DETERMINATION SIGNAL IN C.ELEGANS."

Hodgkin JA, Milne CA

[European Worm Meeting, 1998]

Male and hermaphrodite C.elegans differ significantly at the anatomical and behavioural level. The difference begins in their X chromosome complement. Males have a single X while hermaphrodites have two. It is the assessment of the ratio of X chromosomes to autosome set (1X:2A vs 2X:2A) that sets a C.elegans embryo on a male or hermaphrodite developmental pathway. FOX-1 is an RNP-type RNA-binding protein involved in assessing this ratio. It, along with a few other X-linked genes (often referred to as numerator elements), acts to set the level of activity of xol-1, the regulatory gene at the head of the sex determination pathway. High levels of xol-1 results in male development while low levels results in hermaphrodite development. fox-1 and the other numerators act to down regulate xol-1 activity. FOX-1 appears to act post-transcriptionally as might be expected from an RNA-binding protein. I have identified two alternative transcripts of fox-1, both of which contain the RNA-binding motif. I have shown, using antibodies against FOX-1, that four different forms of FOX-1 can be observed throughout development with one form being predominant in the embryo. Further characterisation of these forms will be discussed with reference to their influence on the state of the sex determination pathway. I have also identified a second putative RNA-binding protein ETR-1 which interacted specifically with FOX-1 in a yeast two-hybrid screen. This protein has similarity to the elav-like family of RNA-binding proteins. It has two RNP motifs in succession at the amino terminus separated from a third by a 280 amino acid tether region. RNAi experiments with this gene result in non-sex specific lethality suggesting etr-1 plays an essential role. Overexpression of the cDNA using a heat shock promoter shows no obvious phenotype. Analysis of the expression pattern using GFP-Lac-Zis underway.

paper:

Milne CA et al. (1999) Curr Biol "ETR-1, a homologue of a protein linked to myotonic dystrophy, is essential for muscle development in Caenorhabditis elegans."

Hodgkin JA, Milne CA

[Curr Biol, 1999]

Post-transcriptional gene processing by RNA-binding proteins (RBPs) has crucial roles during development [1] [2]. Here, we report the identification of ETR-1 (ELAV-type RNA-binding protein), a muscle-specific RBP in the nematode Caenorhabditis elegans. ETR-1 is related to the family of RBPs defined by the protein ELAV, which is essential for neurogenesis in the fruit fly Drosophila; members of the family possess two consecutive RNA recognition motifs (RRMs) separated from a third, carboxy-terminal RRM by a tether region of variable length [3] [4] [5] [6]. Its closest homologue, CUG-binding protein (CUG-bp), is a human RBP that has been implicated in the disease myotonic dystrophy and binds CUG repeats in the 3' untranslated region (UTR) of the mRNA for myotonic dystrophy protein kinase (DMPK) [7] [8]. Inactivation of etr-1 by RNA-mediated interference resulted in embryonic lethality. Embryos failed to elongate and became paralysed, a phenotype characteristic of C. elegans Pat mutants, which are defective in muscle formation and function [9]. The data indicate that etr-1 is essential for muscle development in C. elegans, perhaps by playing a role in post-transcriptional processing of some muscle component, and thus suggesting a possible conservation of gene function with human CUG-bp.

paper:

Milne CA et al. (1997) International C. elegans Meeting "ANALYSIS OF FOX-1, AN RNA-BINDING PROTEIN INVOLVED IN THE PRIMARY SEX DETERMINATION SIGNAL IN C. ELEGANS"

Skipper M, Milne CA, Hodgkin JA

[International C. elegans Meeting, 1997]

person: Catherine Milne

Medical Research Council Laboratory of Molecular Biology; Cambridge, United Kingdom

paper:

CA Milne et al. (1999) International C. elegans Meeting "ETR-1, an elav-type RNA-binding protein with homology to human CUG-bp, is essential for muscle development in C. elegans."

J Hodgkin, CA Milne

[International C. elegans Meeting, 1999]

Post-transcriptional processing of gene products by RNA-binding proteins has been increasingly recognised as an key means of regulating gene expression. A family of RNA-binding proteins with similarity to Drosophila ELAV is one group that has been identified as important for regulating developmental events. Family members have three RNP-type RNA binding motifs, the first two separated from the third by a tether region of approximately 100 amino acids. We previously identified C. elegans ETR-1 in a two-hybrid screen which used FOX-1, an RNP containing protein involved in sex determination, as bait. ETR-1 contains the characteristic arrangement of 3 RNP motifs but has an unusually large, glutamine-rich tether region of 376 amino acids. An etr-1:GFP reporter construct reveals that etr-1 is expressed in muscle precursor cells in the early embryo and in several muscle types including body wall muscle and vulval muscle in the adult. No expression is observed in pharyngeal muscle. RNAi experiments using the unique tether region result in embryonic lethality. Arrested embryos fail to elongate beyond the two-fold stage and have a phenotype similar to that observed for Pat mutant embryos. Pat mutants which have been cloned are known to encode structural components of muscle. Interestingly, the most closely related protein to ETR-1 is human CUG-bp which has been implicated in myotonic muscular dystrophy (DM). CUG-bp is known to bind a CUG-rich region in the intron of chicken TroponinT to regulate alternative splicing and is thought to bind to the CUG expansions in the 3'UTR of DM-protein kinase that are associated with DM. Expression of etr-1 in muscle and the appearance of a Pat phenotype with RNAi suggests that ETR-1 is required for proper muscle development, perhaps by regulating the post-transcriptional processing of one or more of the structural components. The biological relevance of the original physical interaction between ETR-1 and FOX-1 in the two-hybrid screen remains unclear as there is no obvious affect of etr-1 on sex determination. The embryonic expression patterns of the two proteins overlap however and an in vivo interaction cannot be ruled out. Further characterisation of potential targets and the mode of action of C. elegans ETR-1 is underway.

gene class: ncx

Na/Ca eXchangers

paper:

Wang QC et al. (2016) Cell "TMCO1 Is an ER Ca(2+) Load-Activated Ca(2+) Channel."

Li Y, Yang Y, Liu Y, Zhang B, Tang TS, Yu J, Tan H, Chen Q, Wang H, Yang M, Wang X, Zheng Q, Li X, Zhou A, Guo C, Wang F, Wang JQ, Chai H, Sun Z, Wang QC, Zhu S

[Cell, 2016]

Maintaining homeostasis of Ca(2+) stores in the endoplasmic reticulum (ER) is crucial for proper Ca(2+) signaling and key cellular functions. The Ca(2+)-release-activated Ca(2+) (CRAC) channel is responsible for Ca(2+) influx and refilling after store depletion, but how cells cope with excess Ca(2+) when ER stores are overloaded is unclear. We show that TMCO1 is an ER transmembrane protein that actively prevents Ca(2+) stores from overfilling, acting as what we term a "Ca(2+) load-activated Ca(2+) channel" or "CLAC" channel. TMCO1 undergoes reversible homotetramerization in response to ER Ca(2+) overloading anddisassembly upon Ca(2+) depletion and forms a Ca(2+)-selective ion channel on giant liposomes. TMCO1 knockout mice reproduce the main clinical features of human cerebrofaciothoracic (CFT) dysplasia spectrum, a developmental disorder linked to TMCO1 dysfunction, and exhibit severe mishandling of ER Ca(2+) in cells. Our findings indicate that TMCO1 provides a protective mechanism to prevent overfilling of ER stores with Ca(2+) ions.

anatomy term: Ca nucleus

nucleus of pedigree Ca