Connection Between Epigenome, Selective Mutability, Evolution, and Human Disease
Li, Harris et al., PLoS Genetics
Researchers at the Baylor College of Medicine and elsewhere propose a "connection between the epigenome, selective mutability, evolution, and human disease" based on the findings of their study on associations of structural mutability with germline DNA methylation and with non-allelic homologous recombination mediated by low-copy repeats. "Combined evidence from four human sperm methylome maps, human genome evolution, structural polymorphisms in the human population, and previous genomic and disease studies consistently points to a strong association of germline hypomethylation and genomic instability," the Baylor-led team writes.
Going 'Beyond the Genome'
BioMed Central's Beyond the Genome conference in Boston this week — which was held in conjunction with Genome Biology's 10th anniversary — showcased the work of several researchers whose ideas go beyond just sequencing.
The University of Maryland's Steven Salzberg kicked off the conference with a keynote speech about the work he and others are doing to try and accurately estimate exactly how many genes a person has. In 1964, F. Vogel wrote a letter to Nature estimating that humans have 6.7 million genes. He was way off, Salzberg said, but it hasn't gotten any easier over the years to make the estimate more accurate. In the mid-1990s, three different papers estimated the count to be 50,000 to 100,000, 64,000, and 80,000. Even after the draft genome was published, the estimates widely varied. The public consortium estimated the count to be between 30,000 and 40,000, while Celera and its private partners estimated 26,588, with 12,000 other additional "likely" genes. So far, the most accurate estimate is 22,333 human genes, Salzberg said, but there is still much of the human genome that not much is known about, and RNA-seq is still revealing a lot of new genes that may have previously been overlooked. In the end, Salzberg said, it's not as important to know how many genes there are as to know what they are and what they do.
George Church emphasized how important it is to continue to read the genome. About 2,000 genes are highly predictive and medically actionable, he said, and as the price of sequencing continues to drop, researchers will be able to find more genes they can work with to the benefit of human health. Church also stressed the importance of open-access data, and said there is a need for an open database that researchers can use to analyze each others' data.
Elaine Mardis spoke about her work with cancer genomics, and said that, in researching the way tumors work, validating tumor variants is important especially for dissemination of the information to the wider scientific community for further analysis. The speed of data generation is both challenging and enabling, she added.
The University of Washington's Jay Shendure talked about his lab's work with exome sequencing in autism studies. At least some percentage of autism is caused by coding mutations, and exome sequencing is useful in studies of the disorder because the technique can be used to focus in on a single gene instead of an entire region of the genome, Shendure said. He described a trio-based exome study done in his lab, where 60 exomes — from 20 autistic children and both of their parents — were sequenced, and then analyzed to identify Mendelian errors. The researchers found 16 de novo SNPs validated by Sanger from the 20 autism trios, and found two genes — GRIN2B and FOXP1 — which they think could be causative in autism.
The University of Colorado's Rob Knight and BGI's Jun Wang discussed their respective labs' work with microbes. Knight talked about the research he has done with obese and lean mice, and trying to elucidate the relationship between an organism's weight and its gut microbes. Wang talked about some of the studies BGI has done with diabetic patients, and said one study of Chinese type II diabetes patients discovered more than 500,000 novel bacterial genes and found 1,306 bacterial genes associated with diabetic patients, though whether the genes were the cause or the effect of diabetes is not yet known.
It is intriguing that despite
It is intriguing that despite the complete sequencing of the human genome for many years now, it is still unresolved exactly how many human genes actually exist. Mass spectrometry studies have revealed several protein sequences that were not originally described in gene databases. In my own experience, with the assignment of over 90,000 phospho-sites in predicted human proteins for PhosphoNET (www.phosphonet.ca), I have noticed several hundred proteins that were originally documented in UniProt (www.uniprot.org) that have had the entries deleted without any replacements. Since these phosphoproteins were identified from cell lysates by mass spectrometry, obviously the encoding genes actually exist. Since Uniprot has just over 21,000 distinct human proteins currently listed, perhaps 4 to 5 percent of human proteins are still not tracked in the best repository that we have information about our proteins. How well the 22,333 figure for the total number of human genes accounts for these anomalies identified by mass spectrometry analysis of proteins is also unclear.
A better title would be:
A better title would be: "FractoGene Recurses to the Genome". Both "Going beyond the Genome" and "Counting the Exact Number of Genes in Human DNA" are exercises in futility - unless going beyond the genome is tracked through its full recourse from intrinsic and extrinsic proteins back to the DNA>RNA>PROTEINS> and on, as well as contiguous sequences, formerly defined as "genes" yield to facts of their "alternative splicing" (one gene acting as many different genes when spliced in various different ways), as well as to the newly found facts that given contiguous sequences constitutes functional units with sequences very far downstream or upstream, totally outside of the boundaries of the (now obsolete) "gene" definition. The Principle of Recursive Genome Function of our Genome Revolution defines not just one trip to go "beyond Genome" (akin to the Russians in the early days of Space Age, blasting a dog into space and leave it there to perish), but more like "Sending a Man on the Moon - and taking him safely back to Earth" (and do it repeatedly, again and again). It is within the context of recursive algorithms, such as fractal iterative recursion, that seemingly scattered elements of genes, FractoGene governs growth of fractal organelles (such as brain cells), organs (such as the lung) and organisms (such as the cauliflower romanesca) as guided by the demonstrably fractal genome, recursing through epigenomic channels back to the DNA. Pellionisz_at_JunkDNA.com