All posts by bk

Neurosecretory cells in Trichoplax

Endocrinology, Evolution, ,

Trichoplax adhaerens are among the earlier animal precursor on the same lines as sponges (porifera)

from Kleine/Rossmanith Hormone und Hormonsystem, Springer 2014
from Kleine/Rossmanith Hormone und Hormonsystem, © Springer 2014

In a paper in Current Biology (http://dx.doi.org/10.1016/j.cub.2014.05.046) Smith et al. show that this archaic organism has six cell types one of them a neurosecretory cell. This is remarkable since it would be the earliest example of neuroscretory cells. It would also show that neurosecretory cells are one of the primordial cells types in animals before the nerve system became apparent. A FMRF-amide has been suspected in the genome of Trichoplax and its expression is measured with an antibody against FMRF-amides.

We have analyzed the situation further: In the whole genome of Trichoplax was searched for frmfgkr (gkr was added since that would most probably be result in a processed frmf-amide.) A perfect homology was not found. There was , however, one peptide sequence which would give rise to a oligopeptide precursor with more than one peptide-amide (XP_002117813.1). Other protein would fullfil the requirements for a peptide precursor much less stringently:

XP_002117813.1
XP_002117813.1

There are several repeats of nsxsxqqgipsitf (x for variable amino acids) which are separated by gkr as neuropeptides should. These repeats are underlined, the gkr motifs are coulored in red, the homologues sequences are yellow highlighted. The N-terminal peptide has a RR motif in front which would fit a prohormone convertase 2. You may read in Hormon und Hormonsystem about maturation of hormones and neuropeptides.

This sequence is by all criteria a neuropeptde precursor. It is different from FRMF-amides and it is questionable whether the antiserum described in the article would react to it.

HBV – a way to get rid of the virus

Antiviral drug, HBV, Infection,

When the Hepatitis B Virus (HBV) is attacked it remains intracellularly as a covalently closed circular DNA (cccDNA) which can give raise to new viruses. In a Perspective contribution to Science (DOI: 10.1126/science.1252186) Amir Shlomai and Charles M. Rice describe an article by Lucifora et al. (DOI: 10.1126/science.1243462) who found a way to get rid of the cccDNA. These researcher found that interferon-α treatment or action via the lymphotoxin-β receptor activated de-aminination of viral cccDNA which renders the viral DNA inactive and receptive to degradation.

The enzymes triggered in the above described processes are apolipoprotein B mRNA editing enzyme APOBEC3A and APOBEC3B, which only work in conjunction with HBV not HIV. Their presence is necessary in order to elicit a virus depletion in liver cells.

This is good news for 400 Million people infected with HBV since it shows that the virus not only can be kept in charge but eliminated, too.

Pre-eclampsia in a line with Alzheimer, Parkinson, and mad cow disease

Biochemistry, Cell physiology,

In an IN DEPTH contribution in Science Nadia Whitehead describes a Science Translational Medicine article (DOI: 10.1126/scitranslmed.3008808) where a team around the doctors Burimshi analyzed urine from 600 pregnant women using the dye Congo red which stains only “bunched”, not properly folded proteins. Those women with a risk of preeclampsia had bunched proteins with a frequency of more than 80 % while healthy women had none. Among the five proteins mostly bunched were immunoglobulin light chains, ceruloplasmin, SERPINA1, albumin and (sic!) Alsheimer’s β-amyloid. The authors conclude that preeclampsia might also be a disease of protein misfolding.

Aside from a new way to look at the disease which affects about 10 % of birth worldwide this paper offers a cheap test for preeclampsia. Remarcable!

Brain structures and hormones in parents when children are raised

Brain, Circuits, Hormones, Oxytocin

In a comment on a paper in the same issue of PNAS Sarina Saturn describes how Abraham et coworkers have analysed the complex relationship of neural activation, hormones and behaviour in first time parents comparing primary care /PC) mothers and secondary care (SC) fathers who are partners of mothers and primary care (PC) fathers who raise a child without a mother.

Abraham  et al. have identified characteristic features common to fathers and mothers and, not surprisingly, also features where mothers and fathers differ. An emotional network including  the amygdala (AMY),* ventral anterior cingulate cortex (vACC),* insula,* inferior frontal gyrus (IFG), and ventral tegmental area (VTA).* *Subcortical and paralimbic structures not located at the outer cortical surface was found as well as a mentalizing network which includes superior temporal sulcus (STS), frontopolar cortex (FPC), ventromedial prefrontal cortex (vmPFC), and temporal poles (TP).  Cites from PNAS:

PC-mothers displayed the greatest activation of the emotional system, and this activation significantly related to parent–infant synchrony and oxytocin levels. SC-fathers, in contrast, exhibited more activation of the cortical system. Fascinatingly, PC-fathers showed amygdala activation similar to PC-mothers and STS activation similar to SC-fathers, with pronounced functional connectivity between the two regions. This suggests that when a baby is raised by PC-fathers, both systems are used for optimal childrearing.

For both PC-fathers and SC-fathers, the STS–amygdala overlap directly related to how much the men were involved in tending to the baby, and STS activation correlated with oxytocin levels and parent–infant synchrony. This provides evidence that exposure to the infants and caretaking activities can groom oxytocin and neural systems to carry out the degree of paternal involvement.

This is a first time that these interactions have been studied. Nicely done!

When Africans met Neanderthals some 50000 years ago: war and rape

Evolution, Genetics, History, Human evolution

There is an very interesting paper in Nature (doi:10.1038/nature12961) about the Neanderthal genom part in modern men. It shows an a chromosome by chromosome demonstration how much of the Neanderthal ancestry is found in the autosomes and in the sex chromosome: about 1 % in autosome and considerable less in sex chromomes. In the Y-chromosome it is barely found.

When the two populations first encounterd some 50000 years ago (as a paper form PLOS suggested: DOI: 10.1371/journal.pgen.1002947) we can envisage how this was done:  there was war and the Neanderthal female were raped after the man were killed. Whether this was a singular event or repeatingly done in the clash of general war betweem the two species is not documented, but when the progeny e.g. was selected for the “African” phenotyp then the Neatherthal would be not maintained in the Y chromosome.

Very suggestive! And much has not changed till modern times

The early history of man

Evolution, Human evolution

A review in Science (DOI: 10.1126/science.1236828) deals with the human evolution 3 to 1.5 x 106 years ago. The aridity in Africa is supposed to drive expansion to other continents. Several parallel  lineages were present. You may find this review  at the local university or in an (English) bookshop.

The repertoire of smelling

Cell physiology, Olfactory system

In a Science article (DOI: 10.1126/science.1249168) C. Bushdid, M. O. Magnasco, L. B. Vosshall, A. Keller determine the size of the olfactory repertoire. On the basis of psychological testing they find that the human nose can distinguish at least 1 Billion (european enumeration = 1012) In the English nomenclature leaving out Milliarde (109) this is even more impressive: 1 Trillion. I wonder about the number of chemically defined receptors. In the case of the immune systems the repertoire of B and T cells (1012) could finally be explained by recombination. What the olfactory system has in its stores is to be seen. This paper sets the threshold fairly high.

IgD puzzle solved

B cell, Immunology

For years it has been known that B lymphocytes express either IgM and IgM/IgD. It was unknown how B cells are triggered to express IgD additionally. A paper in PNAS  (doi: 10.1073/pnas.1402739111) now demonstrates that a so far overlooked Zinc-finger protein (ZFP318) is responsible for the alternative splicing in the B cell thus driving expression of IgD.

Tibetans are different!

Biochemistry, Cell physiology, Evolution, Human evolution

A paper in Nature (Altitude adaptation in Tibetans caused by introgression of Denisovan-like DNA Emilia Huerta-Sánchez, Xin Jin, Asan et al.) says that DNA in Tibetans to adapt to the altitude can be attributed to an extinguished hominid precursor, the Denisovan: (cited from Nature)

Admixture with other hominin species helped humans to adapt to high-altitude environments; the EPAS1 gene in Tibetan individuals has an unusual haplotype structure that probably resulted from introgression of DNA from Denisovan or Denisovan-related individuals into humans, and this haplotype is only found in Denisovans and Tibetans, and at low frequency among Han Chinese.